Highlights
Nowadays, extreme electromagnetic pulses with fewcycle durations are routinely produced in optical labs [1]. They are used for dispersion measurements, spectroscopy, optical communication, and as widespectrum light sources. More exotic applications include the optical realization of event horizons in analogy to black and white holes, optical clocks, control of chemical reactions, and the measurement of fundamental physical constants [2,3,4].
The physics of ultrashort pulses creates new mathematical challenges, since the underlying multiscale phenomena need to be described by effective models that allow for an efficient numerical treatment. The common slowly varying envelope approximation is no longer valid for the range of pulse widths that are presently available [5]. New models have to be developed. Currently, such models either assume a specific shape for the medium dispersion (e.g., a short pulse equation [6]), or represent the dispersion profile by a nonbounded polynomial function (a generalized nonlinear Schrödinger equation [7]). However, these models ignore some basic physical constraints (e.g., the causality principle) and may introduce huge errors for spectrally wide pulses [5].
The pulse propagation models worked out at WIAS take advantage of two major improvements: Firstly, the systematic use of rational approximations for the medium dispersion functions allows to describe nonlocal effects, to control dispersion asymptotically for large frequencies, and to satisfy the causality principle [8]. The second advantage is the application of classical creation and annihilation operators for photons [9]. Due to this, simple firstorder propagation equations with minimal approximations can be obtained. These equations can easily be solved by straightforwardly applying the splitstep Fourier method [10].
Fig. 1: Left: a solitary pulse (red) is compressed by a pump pulse (blue). Middle: controlling of light by light requires a nearly perfect group velocity matching. Right: an exemplary 7th increase of the pulse peak power.
A topic of special interest is controlling light by light for effective manipulation of optical pulses (Fig.1). A pair of group velocity matched pulses can be used for alloptical switching [11], supercontinuum generation [12], and pulse compression [13]. Quantitative multiscale theory of such interactions was developed in [14,15].
 [1] T. Brabec and F. Krausz, Rev. Mod. Phys. 72, 545 (2000)
 [2] Max Planck Institute of Quantum Optics, Laboratory for Attosecond Physics
 [3] Weizmann Institute of Science. Ulf Leonhardt's group, Geometry and light
 [4] Florian Aigner, Steering chemical reactions with laser pulses
 [5] K. E. Oughstun and H. Xiao, Phys. Rev. Lett. 78, 642 (1997)
 [6] T. Schäfer and C. E. Wayne, Physica D 196, 90 (2004)
 [7] J. M. Dudley, G. Genty, S. Coen, Rev. Mod. Phys. 78, 1135 (2006)
 [8] S. Amiranashvili, U. Bandelow, A. Mielke, Opt. Commun. 283, 480 (2010)
 [9] S. Amiranashvili and A. Demircan, Phys. Rev. A 82, 013812 (2010)
 [10] S. Amiranashvili, R. Čiegis, M. Radziunas, Kinetic and Related Models 8, 215 (2015)
 [11] A. Demircan, S. Amiranashvili, G. Steinmeyer, Phys. Rev. Lett. 106, 163901 (2011)
 [12] A. Demircan, S. Amiranashvili, C. Brée, G. Steinmeyer, Phys. Rev. Lett. 110, 233901 (2013)
 [13] A. Demircan, S. Amiranashvili, C. Brée, U. Morgner, G. Steinmeyer, Opt. Lett. 39, 2735 (2014)
 [14] S. Pickartz, U. Bandelow, S. Amiranashvili, Phys. Rev. A 94, 033811 (2016)
 [15] S. Pickartz, U. Bandelow, S. Amiranashvili, Opt. Lett. 42, 1416 (2017)
Publications
Monographs

S. Amiranashvili, Chapter 6: Hamiltonian Framework for Short Optical Pulses, in: New Approaches to Nonlinear Waves, E. Tobisch, ed., 908 of Lecture Notes in Physics, Springer International Publishing Switzerland, Cham, 2016, pp. 153196, (Chapter Published).
Abstract
Physics of short optical pulses is an important and active research area in nonlinear optics. In what follows we theoretically consider the most extreme representatives of short pulses that contain only several oscillations of electromagnetic field. Description of such pulses is traditionally based on envelope equations and slowly varying envelope approximation, despite the fact that the envelope is not ?slow? and, moreover, there is no clear definition of such a ?fast? envelope. This happens due to another paradoxical feature: the standard (envelope) generalized nonlinear Schrödinger equation yields very good correspondence to numerical solutions of full Maxwell equations even for fewcycle pulses, a thing that should not be. In what follows we address ultrashort optical pulses using Hamiltonian framework for nonlinear waves. As it appears, the standard optical envelope equation is just a reformulation of general Hamiltonian equations. In a sense, no approximations are required, this is why the generalized nonlinear Schrödinger equation is so effective. Moreover, the Hamiltonian framework greatly contributes to our understanding of ”fast” envelope, ultrashort solitons, stability and radiation of optical pulses. Even the inclusion of dissipative terms is possible making the Hamiltonian approach an universal theoretical tool also in extreme nonlinear optics. 
H.J. Wünsche, J. Piprek, U. Bandelow, H. Wenzel, eds., Proceedings of the 5th International Conference on ``Numerical Simulation of Optoelectronic Devices'' (NUSOD '05) in Berlin, September 1922, 2005, IEEE, Piscataway, NJ, 2005, 134 pages, (Collection Published).
Articles in Refereed Journals

C. Brée, M. Hofmann, I. Babushkin, A. Demircan, U. Morgner, O.G. Kosareva, A.B. Savel'ev, A. Husakou, M. Ivanov, Symmetry breaking and strong persistent plasma currents via resonant destabilization of atoms, Physical Review Letters, 119 (2017), pp. 243202/1243202/5, DOI 10.20347/WIAS.PREPRINT.2423 .
Abstract
The ionization rate of an atom in a strong optical field can be resonantly enhanced by the presence of longliving atomic levels (so called Freeman resonances). This process is most prominent in the multiphoton ionization regime meaning that ionization event takes many optical cycles. Nevertheless, here we show that these resonances can lead to fast subcyclescale plasma buildup at the resonant values of the intensity in the pump pulse. The fast buildup can break the cycletocycle symmetry of the ionization process, resulting in generation of persistent macroscopic plasma currents which remain after the end of the pulse. This, in turn, gibes rise to a broadband radiation of unusual spectral structure forming a comb from terahertz (THz) to visible. This radiation contains fingerprints of the attosecond electronic dynamics in Rydberg states during ionization. 
C. Brée, I. Babushkin, U. Morgner, A. Demircan, Regularizing aperiodic cycles of resonant radiation in filament light bullets, Physical Review Letters, 118 (2017), pp. 163901/1163901/5, DOI 10.20347/WIAS.PREPRINT.2394 .
Abstract
We demonstrate an up to now unrecognized and very effective mechanism which prevents filament collapse and allows persistent selfguiding propagation retaining larg portion of the optical energy onaxis over unexpected long distances. The key ingredient is the possibility of leaking continuously energy into the normal dispersion regime via emission of resonant radiation. The frequency of the radiation is determined by the dispersion dynamically modified by photogenerated plasma, thus allowing to excite new frequencies in the spectral ranges which are otherwise difficult to access. 
G. Slavcheva, M.V. Koleva, A. Pimenov, The impact of microcavity wire width on polariton soliton existence and multistability, Journal of Optics, 19 (2017), pp. 065404/1065404/15, DOI 10.20347/WIAS.PREPRINT.2381 .
Abstract
We have developed a model of the nonlinear polariton dynamics in realistic 3D nonplanar microcavity wires in the drivendissipative regime [15]. We find that the typical microcavity optical bistability evolves into multistability upon variation of the model parameters. The origin of the multistability is discussed in detail. We apply linear perturbation analysis to modulational instabilities, and identify conditions for localisation of composite multimode polariton solitons in the triggered parametric oscillator regime. Further, we demonstrate stable polariton soliton propagation in tilted and tapered waveguides, and determine maximum tilt angles for which solitons are still found. Additionally, we study soliton amplitude and velocity dependence on the wire width, with a view towards device applications. 
D. Puzyrev, A.G. Vladimirov, A. Pimenov, S.V. Gurevich, S. Yanchuk, Bound pulse trains in arrays of coupled spatially extended dynamical systems, Physical Review Letters, 119 (2017), pp. 163901/1163901/6, DOI 10.1103/PhysRevLett.119.163901 .
Abstract
We study the dynamics of an array of nearestneighbor coupled spatially distributed systems each generating a periodic sequence of short pulses. We demonstrate that, unlike a solitary system generating a train of equidistant pulses, an array of such systems can produce a sequence of clusters of closely packed pulses, with the distance between individual pulses depending on the coupling phase. This regime associated with the formation of locally coupled pulse trains bounded due to a balance of attraction and repulsion between them is different from the pulse bound states reported earlier in different laser, plasma, chemical, and biological systems. We propose a simplified analytical description of the observed phenomenon, which is in good agreement with the results of direct numerical simulations of a model system describing an array of coupled modelocked lasers. 
I. Babushkin, C. Brée, Ch.M. Dietrich, A. Demircan, U. Morgner, A. Husakou, Terahertz and higherorder Brunel harmonics: From tunnel to multiphoton ionization regime in tailored fields, Journal of Modern Optics, (2017), pp. 110, DOI 10.1080/09500340.2017.1285066 .
Abstract
Brunel radiation appears as a result of a twostep process of photoionization and subsequent acceleration of electron, without the need of electron recollision. We show that for generation of Brunel harmonics at all frequencies, the subcycle ionization dynamics is of critical importance. Namely, such harmonics disappear at the low pump intensities when the ionization dynamics depends only on the slow envelope (socalled multiphoton ionization regime) and not on the instantaneous field. Nevertheless, if the pump pulse contains incommensurate frequencies, Brunel mechanism does generate new frequencies even in the multiphoton ionization regime. 
N. Raabe, T. Feng, T. Witting, A. Demircan, C. Brée, G. Steinmeyer, Role of intrapulse coherence in carrierenvelope phase stabilization, Physical Review Letters, 119 (2017), pp. 123901/1123901/5, DOI 10.1103/PhysRevLett.119.123901 .
Abstract
The concept of coherence is of fundamental importance for describing the physical characteristics of light and for evaluating the suitability for experimental application. In the case of pulsed laser sources, the pulsetopulse coherence is usually considered for a judgment of the compressibility of the pulse train. This type of coherence is often lost during propagation through a highly nonlinear medium, and pulses prove incompressible despite multioctave spectral coverage. Notwithstanding the apparent loss of interpulse coherence, however, supercontinua enable applications in precision frequency metrology that rely on coherence between different spectral components within a laser pulse. To judge the suitability of a light source for the latter application, we define an alternative criterion, which we term intrapulse coherence. This definition plays a limiting role in the carrierenvelope phase measurement and stabilization of ultrashort pulses. It is shown by numerical simulation and further corroborated by experimental data that filamentationbased supercontinuum generation may lead to a loss of intrapulse coherence despite nearperfect compressibility of the pulse train. This loss of coherence may severely limit active and passive carrierenvelope phase stabilization schemes and applications in optical highfield physics. 
S. Pickartz, C. Brée, U. Bandelow, S. Amiranashvili, Cancellation of Raman selffrequency shift for compression of optical pulses, Optical and Quantum Electronics, 49 (2017), pp. 328/1328/7, DOI 10.1007/s1108201711647 .
Abstract
We study to which extent a fiber soliton can be manipulated by a specially chosen continuous pump wave. A group velocity matched pump scatters at the soliton, which is compressed due to the energy/momentum transfer. As the pump scattering is very sensitive to the velocity matching condition, soliton compression is quickly destroyed by the soliton selffrequency shift (SSFS). This is especially true for ultrashort pulses: SSFS inevitably impairs the degree of compression. We demonstrate numerically that soliton enhancement can be restored to some extent and the compressed soliton can be stabilized, provided that SSFS is canceled by a second pump wave. Still the available compression degree is considerably smaller than that in the Ramanfree nonlinear fibers. 
S. Pickartz, U. Bandelow, S. Amiranashvili, Asymptotically stable compensation of soliton selffrequency shift, Optics Letters, 42 (2017), pp. 14161419, DOI 10.20347/WIAS.PREPRINT.2343 .
Abstract
We report the cancellation of the soliton selffrequency shift in nonlinear optical fibers. A soliton which interacts with a group velocity matched low intensity dispersive pump pulse, experiences a continuous blueshift in frequency, which counteracts the soliton selffrequency shift due to Raman scattering. The soliton selffrequency shift can be fully compensated by a suitably prepared dispersive wave.We quantify this kind of solitondispersive wave interaction by an adiabatic approach and demonstrate that the compensation is stable in agreement with numerical simulations. 
M. Hofmann, C. Brée, Adiabatic Floquet model for the optical response in femtosecond filaments, Journal of Physics B: Atomic, Molecular and Optical Physics, 49 (2016), pp. 205004/1205004/12.
Abstract
The standard model of femtosecond filamentation is based on phenomenological assumptions which suggest that the ionizationinduced carriers can be treated as free according to the Drude model, while the nonlinear response of the bound carriers follows the alloptical Kerr effect. Here, we demonstrate that the additional plasma generated at a multiphoton resonance dominates the saturation of the nonlinear refractive index. Since resonances are not captured by the standard model, we propose a modification of the latter in which ionization enhancements can be accounted for by an ionization rate obtained from nonHermitian Floquet theory. In the adiabatic regime of long pulse envelopes, this augmented standard model is in excellent agreement with direct quantum mechanical simulations. Since our proposal maintains the structure of the standard model, it can be easily incorporated into existing codes of filament simulation. 
N. Akhmediev, B. Kibler, F. Baronio, M. Belić, W.P. Zhong, Y. Zhang, W. Chang, J.M. SotoCrespo, P. Vouzas, P. Grelu, C. Lecaplain, K. Hammani, S. Rica, A. Picozzi, M. Tlidi, K. Panajotov, A. Mussot, A. Bendahmane, P. Szriftgiser, G. Genty, J. Dudley, A. Kudlinski, A. Demircan, U. Morgner, S. Amiranashvili, C. Brée, G. Steinmeyer, C. Masoller, N.G.R. Broderick, A.F.J. Runge, M. Erkintalo, S. Residori, U. Bortolozzo, F.T. Arecchi, S. Wabnitz, C.G. Tiofack, S. Coulibaly, M. Taki, Roadmap on optical rogue waves and extreme events, Journal of Optics, 18 (2016), pp. 137.
Abstract
The pioneering paper “Optical rogue waves" by Solli et al (2007 Nature 450 1054) started the new subfield in optics. This work launched a great deal of activity on this novel subject. As a result, the initial concept has expanded and has been enriched by new ideas. Various approaches have been suggested since then. A fresh look at the older results and new discoveries has been undertaken, stimulated by the concept of ?optical rogue waves?. Presently, there may not by a unique view on how this new scientific term should be used and developed. There is nothing surprising when the opinion of the experts diverge in any new field of research. After all, rogue waves may appear for a multiplicity of reasons and not necessarily only in optical fibers and not only in the process of supercontinuum generation. We know by now that rogue waves may be generated by lasers, appear in wide aperture cavities, in plasmas and in a variety of other optical systems. Theorists, in turn, have suggested many other situations when rogue waves may be observed. The strict definition of a rogue wave is still an open question. For example, it has been suggested that it is defined as ?an optical pulse whose amplitude or intensity is much higher than that of the surrounding pulses?. This definition (as suggested by a peer reviewer) is clear at the intuitive level and can be easily extended to the case of spatial beams although additional clarifications are still needed. An extended definition has been presented earlier by N Akhmediev and E Pelinovsky (2010 Eur. Phys. J. Spec. Top. 185 1?4). Discussions along these lines are always useful and all new approaches stimulate research and encourage discoveries of new phenomena. Despite the potentially existing disagreements, the scientific terms ?optical rogue waves? and ?extreme events? do exist. Therefore coordination of our efforts in either unifying the concept or in introducing alternative definitions must be continued. From this point of view, a number of the scientists who work in this area of research have come together to present their research in a single review article that will greatly benefit all interested parties of this research direction. Whether the authors of this “roadmap" have similar views or different from the original concept, the potential reader of the review will enrich their knowledge by encountering most of the existing views on the subject. Previously, a special issue on optical rogue waves (2013 J. Opt. 15 060201) was successful in achieving this goal but over two years have passed and more material has been published in this quickly emerging subject. Thus, it is time for a roadmap that may stimulate and encourage further research. 
A. Ankiewicz, D.J. Kedziora, A. Chowdury, U. Bandelow, N. Akhmediev, Infinite hierarchy of nonlinear Schrödinger equations and their solutions, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 93 (2016), pp. 012206/1012206/10.
Abstract
We study the infinite integrable nonlinear Schrödinger equation hierarchy beyond the LakshmananPorsezianDaniel equation which is a particular (fourthorder) case of the hierarchy. In particular, we present the generalized Lax pair and generalized soliton solutions, plane wave solutions, Akhmediev breathers, KuznetsovMa breathers, periodic solutions, and rogue wave solutions for this infiniteorder hierarchy. We find that ?even order? equations in the set affect phase and ?stretching factors? in the solutions, while ?oddorder? equations affect the velocities. Hence oddorder equation solutions can be real functions, while evenorder equation solutions are always complex. 
I. Babushkin, S. Amiranashvili, C. Brée, U. Morgner, G. Steinmeyer, A. Demircan, The effect of chirp on pulse compression at a group velocity horizon, IEEE Photonics Journal, 8 (2016), pp. 7803113/17803113/14, DOI 10.1109/JPHOT.2016.2570001 .
Abstract
Groupvelocity matched crossphase modulation between a fundamental soliton and a dispersive wavepacket has been previously suggested for optical switching applications similar to an optical transistor. Moreover, the nonlinear interaction in the resulting groupvelocity horizon can be exploited for adiabatic compression of the soliton down into the fewcycle regime. Here we show that both mechanisms can be combined. In such a transient compressor, parameters of the dispersive wave may then serve to actively control the soliton compression and adjust the pulse duration in the presence of disturbances. While a certain amount of control is already enabled by the delay between soliton and dispersive wave, the means of controlling the compression process are substantially enhanced by additionally manipulating the chirp of the dispersive wave. Moreover, controlling the chirp of the dispersive wave also enables correction for limitations of the compression scheme due to a selffrequency shift of the soliton or for uncompensated dispersion in the scheme. This substantially widens the practicality of the compression scheme and other applications of the highly efficient nonlinear interaction at the groupvelocity horizon. 
S. Birkholz, C. Brée, I. Veselić, A. Demircan, G. Steinmeyer, Ocean rogue waves and their phase space dynamics in the limit of a linear interference model, Scientific Reports, 6 (2016), pp. 35207/135207/8.
Abstract
We reanalyse the probability for formation of extreme waves using the simple model of linear interference of a finite number of elementary waves with fixed amplitude and random phase fluctuations. Under these model assumptions no rogue waves appear when less than 10 elementary waves interfere with each other. Above this threshold rogue wave formation becomes increasingly likely, with appearance frequencies that may even exceed longterm observations by an order of magnitude. For estimation of the effective number of interfering waves, we suggest the GrassbergerProcaccia dimensional analysis of individual time series. For the ocean system, it is further shown that the resulting phase space dimension may vary, such that the threshold for rogue wave formation is not always reached. Time series analysis as well as the appearance of particular focusing wind conditions may enable an effective forecast of such roguewave prone situations. In particular, extracting the dimension from ocean time series allows much more specific estimation of the rogue wave probability. 
S. Pickartz, U. Bandelow, S. Amiranashvili, Adiabatic theory of solitons fed by dispersive waves, Physical Review A, 94 (2016), pp. 033811/1033811/12.
Abstract
We consider scattering of smallamplitude dispersive waves at an intense optical soliton which constitutes a nonlinear perturbation of the refractive index. Specifically, we consider a singlemode optical fiber and a group velocity matched pair: an optical soliton and a nearly perfectly reflected dispersive wave, a fiberoptical analogue of the event horizon. By combining (i) an adiabatic approach that is used in soliton perturbation theory and (ii) scattering theory from Quantum Mechanics, we give a quantitative account for the evolution of all soliton parameters. In particular, we quantify the increase in the soliton peak power that may result in spontaneous appearance of an extremely large, socalled champion soliton. The presented adiabatic theory agrees well with the numerical solutions of the pulse propagation equation. Moreover, for the first time we predict the full frequency band of the scattered dispersive waves and explain an emerging caustic structure in the spacetime domain. 
S. Pickartz, U. Bandelow, S. Amiranashvili, Efficient alloptical control of solitons, Optical and Quantum Electronics, 48 (2016), pp. 503/1503/7.
Abstract
We consider the phenomenon of an optical soliton controlled (eg. amplified) by a much weaker second pulse which is efficiently scattered at the soliton. An important problem in this context is to quantify the small range of parameters at which the interaction takes place. This has been achieved by using adiabatic ODEs for the soliton characteristics, which is much faster than an empirical scan of the full propagation equations for all parameters in question. 
C. Brée, G. Steinmeyer, I. Babushkin, U. Morgner, A. Demircan, Controlling formation and suppression of fiberoptical rogue waves, Optics Letters, 41 (2016), pp. 35153518.
Abstract
Fiberoptical rogue waves appear as rare but extreme events during optical supercontinuum generation in photonic crystal fibers. This process is typically initiated by the decay of a highorder fundamental soliton into fundamental solitons. Collisions between these solitons as well as with dispersive radiation affect the soliton trajectory in frequency and time upon further propagation. Launching an additional dispersive wave at carefully chosen delay and wavelength enables statistical manipulation of the soliton trajectory in such a way that the probability of rogue wave formation is either enhanced or reduced. To enable efficient control, parameters of the dispersive wave have to be chosen to allow trapping of dispersive radiation in the nonlinear index depression created by the soliton. Under certain conditions, direct manipulation of soliton properties is possible by the dispersive wave. In other more complex scenarios, control is possible via increasing or decreasing the number of intersoliton collisions. The control mechanism reaches a remarkable efficiency, enabling control of relatively large soliton energies. This scenario appears promising for highly dynamic alloptical control of supercontinua. 
S. Amiranashvili , R. Čiegis, M. Radziunas, Numerical methods for generalized nonlinear Schrödinger equations, Kinetic and Related Models, 8 (2015), pp. 215234.
Abstract
We present and analyze different splitting algorithms for numerical solution of the both classical and generalized nonlinear Schrödinger equations describing propagation of wave packets with special emphasis on applications to nonlinear fiberoptics. The considered generalizations take into account the higherorder corrections of the linear differential dispersion operator as well as the saturation of nonlinearity and the selfsteepening of the field envelope function. For stabilization of the pseudospectral splitting schemes for generalized Schrödinger equations a regularization based on the approximation of the derivatives by the low number of Fourier modes is proposed. To illustrate the theoretically predicted performance of these schemes several numerical experiments have been done. 
M. Hofmann, J. Hyyti, S. Birkholz, M. Bock, S.K. Das, R. Grunwald, M. Hoffmann, T. Nagy, A. Demircan, M. Jupé, D. Ristau, U. Morgner, C. Brée, M. Wörner, Th. Elsaesser, G. Steinmeyer, Noninstantaneous polarization dynamics in dielectric media, Optica, 2 (2015), pp. 151157.
Abstract
Thirdorder optical nonlinearities play a vital role for generation and characterization of some of the shortest optical pulses to date, for optical switching applications, and for spectroscopy. In many cases, nonlinear optical effects are used far off resonance, and then an instantaneous temporal response is expected. Here, we show for the first time resonant frequencyresolved optical gating measurements that indicate substantial nonlinear polarization relaxation times up to 6.5,fs in dielectric media, i.e., significantly beyond the shortest pulses directly available from commercial lasers. These effects are among the fastest effects observed in ultrafast spectroscopy. Numerical solutions of the timedependent Schrödinger equation are in excellent agreement with experimental observations. The simulations indicate that pulse generation and characterization in the ultraviolet may be severely affected by this previously unreported effect. Moreover, our approach opens an avenue for application of frequencyresolved optical gating as a highly selective spectroscopic probe in highfield physics. 
M. Hofmann, C. Brée, Femtosecond filamentation by intensity clamping at a Freeman resonance, Physical Review A, 92 (2015), pp. 013813/1013813/7.

G. Slavcheva, A.V. Gorbach, A. Pimenov, A.G. Vladimirov, D. Skryabin, Multistability and polariton formation in microcavity polaritonic waveguides, Optics Letters, 40 (2015), pp. 17871790.
Abstract
Nonlinear polaritons in microcavity waveguides are demonstrated to exhibit multistable behaviour and rich dynamics, including filamentation and soliton formation. We find that the multistability originates from coexistense of different transverse modes of the po laritonic waveguide. Modulational stability and conditions for multimode polariton solitons are studied. Soliton propagation in tilted, relative to the pump momentum, waveguides is demonstrated and a critical tilt angle for the soliton propagation is found. 
S. Birkholz, C. Brée, A. Demircan, G. Steinmeyer, Predictability of rogue events, Physical Review Letters, 114 (2015), pp. 213901/1213901/5.

C. Brée, M. Kretschmar, T. Nagy, H.G. Kurz, U. Morgner, M. Kovačev, Impact of spatial inhomogeneities on onaxis pulse reconstruction in femtosecond filaments, Journal of Physics B: Atomic, Molecular and Optical Physics, 48 (2015), pp. 094002/1094002/6.
Abstract
We demonstrate a strong influence of the spatial beam profile on the vacuumpropagated onaxis pulse shapes for a femtosecond filament in argon. The effects can be minimized by transmitting the filament into the farfield by a laserdrilled pinhole setup. Using this method, we can monitor the pulse compression dynamics along the entire longitudinal extension of the filament, including the ionizationinduced plasma channel. 
S. Amiranashvili, U. Bandelow, N. Akhmediev, Spectral properties of limiting solitons in optical fibers, Optics Express, 22 (2014), pp. 3025130256.
Abstract
It seems to be selfevident that stable optical pulses cannot be considerably shorter than a single oscillation of the carrier field. From the mathematical point of view the solitary solutions of pulse propagation equations should loose stability or demonstrate some kind of singular behavior. Typically, an unphysical cusp develops at the soliton top, preventing the soliton from being too short. Consequently, the power spectrum of the limiting solution has a special behavior: the standard exponential decay is replaced by an algebraic one. We derive the shortest soliton and explicitly calculate its spectrum for the socalled short pulse equation. The latter applies to ultrashort solitons in transparent materials like fused silica that are relevant for optical fibers. 
S. Amiranashvili, U. Bandelow, N. Akhmediev, Ultrashort optical solitons in transparent nonlinear media with arbitrary dispersion, Optical and Quantum Electronics, 46 (2014), pp. 12331238.
Abstract
We consider the propagation of ultrashort optical pulses in nonlinear fibers and suggest a new theoretical framework for the description of pulse dynamics and exact characterization of solitary solutions. Our approach deals with a proper complex generalization of the nonlinear Maxwell equations and completely avoids the use of the slowly varying envelope approximation. The only essential restriction is that fiber dispersion does not favor both the socalled Cherenkov radiation, as well as the resonant generation of the third harmonics, as these effects destroy ultrashort solitons. Assuming that it is not the case, we derive a continuous family of solitary solutions connecting fundamental solitons to nearly singlecycle ultrashort ones for arbitrary anomalous dispersion and cubic nonlinearity. 
R.M. Arkhipov, I. Babushkin, M.K. Lebedev, Y.A. Tolmachev, M.V. Arkhipov, Transient Cherenkov radiation from an inhomogeneous string excited by an ultrashort laser pulse at superluminal velocity, Physical Review A, 89 (2014), pp. 043811/1043811/10.
Abstract
An optical response of onedimensional string made of dipoles with a periodically varying density excited by a spot of light moving along the string at the superluminal (subluminal) velocity is studied. We consider in details the spectral and temporal dynamics of the Cherenkov radiation, which occurs in such system in the transient regime. We point out the resonance character of radiation and the appearance of a new Dopplerlike frequency in the spectrum of the transient Cherenkov radiation. Possible applications of the effect as well as different string topologies are discussed 
A. Demircan, S. Amiranashvili, C. Brée, U. Morgner, G. Steinmeyer, Adjustable pulse compression scheme for generation of fewcycle pulses in the midinfrared, Optics Letters, 39 (2014), pp. 27352738.
Abstract
An novel adjustable adiabatic soliton compression scheme is presented, enabling a coherent pulse source with pedestalfree fewcycle pulses in the infrared or midinfrared regime. This scheme relies on interaction of a dispersive wave and a soliton copropagating at nearly identical group velocities in a fiber with enhanced infrared transmission. The compression is achieved directly in one stage, without necessity of an external compensation scheme. Numerical simulations are employed to demonstrate this scheme for silica and fluoride fibers, indicating ultimate limitations as well as the possibility of compression down to the singlecycle regime. Such output pulses appear ideally suited as seed sources for parametric amplification schemes in the midinfrared. 
A. Demircan, U. Morgner, S. Amiranashvili, C. Brée, G. Steinmeyer, Supercontinuum generation by multiple scatterings at a group velocity horizon, Optics Express, 22 (2014), pp. 38663879.
Abstract
A new scheme for supercontinuum generation covering more than one octave and exhibiting extraordinary high coherence properties has recently been proposed in Phys. Rev. Lett. bf 110, 233901 (2013). The scheme is based on twopulse collision at a group velocity horizon between a dispersive wave and a soliton. Here we demonstrate that the same scheme can be exploited for the generation of supercontinua encompassing the entire transparency region of fused silica, ranging from 300 to 2300nm. At this bandwidth extension, the Raman effect becomes detrimental, yet may be compensated by using a cascaded collision process. Consequently, the high degree of coherence does not degrade even in this extreme scenario. 
M. Kretschmar, C. Brée, T. Nagy, A. Demircan, M. Kovačev, Direct observation of pulse dynamics and selfcompression along a femtosecond filament, Optics Express, 22 (2014), pp. 2290522916.

S. Amiranashvili, U. Bandelow, N. Akhmediev, Fewcycle optical solitary waves in nonlinear dispersive media, Physical Review A, 87 (2013), pp. 013805/1013805/8.
Abstract
We study the propagation of fewcycle optical solitons in nonlinear media with an anomalous, but otherwise arbitrary, dispersion and a cubic nonlinearity. Our approach does not derive from the slowly varying envelope approximation. The optical field is derived directly from Maxwell's equations under the assumption that generation of the third harmonic is a nonresonant process or at least cannot destroy the pulse prior to inevitable linear damping. The solitary wave solutions are obtained numerically up to nearly singlecycle duration using the spectral renormalization method originally developed for the envelope solitons. The theory explicitly distinguishes contributions between the essential physical effects such as higherorder dispersion, selfsteepening, and backscattering, as well as quantifies their influence on ultrashort optical solitons. 
I. Omelchenko, O. Omel'chenko, P. Hövel, E. Schöll, When nonlocal coupling between oscillators becomes stronger: Patched synchrony or multichimera states, Physical Review Letters, 110 (2013), pp. 224101/1224101/5.
Abstract
Systems of nonlocally coupled oscillators can exhibit complex spatiotemporal patterns, called chimera states, which consist of coexisting domains of spatially coherent (synchronized) and incoherent dynamics. We report on a novel form of these states, found in a widely used model of a limitcycle oscillator if one goes beyond the limit of weak coupling typical for phase oscillators. Then patches of synchronized dynamics appear within the incoherent domain giving rise to a multichimera state. We find that, depending on the coupling strength and range, different multichimera states arise in a transition from classical chimera states. The additional spatial modulation is due to strong coupling interaction and thus cannot be observed in simple phaseoscillator models 
M.V. Arkhipov, R.M. Arkhipov, S.A. Pulkin, Effects of inversionless oscillation in twolevel media from the point of view of specificities of the spatiotemporal propagation dynamics of radiation, Optics and Spectroscopy, 114 (2013), pp. 831837.
Abstract
We report the results of computer simulation of the emission of radiation by an extended twolevel medium in a ring cavity. The cases of using strong external monochromatic, quasimonochromatic, and biharmonic radiation for pumping the twolevel medium are analyzed. It is shown that the emission of radiation with spectral content different from that of the pump radiation, which is interpreted as the inversionless oscillation, is the result of the spatiotemporal dynamics of light propagation in an extended twolevel medium imbedded in a cavity. The appearance of this radiation is not related to known resonances of amplification of a weak probe field in a thin layer of the twolevel system (the effect of inversionless oscillation) induced by strong resonance monochromatic or biharmonic field, as was thought before. 
A. Demircan, S. Amiranashvili, C. Brée, G. Steinmeyer, Compressible octave spanning supercontinuum generation by twopulse collisions, Physical Review Letters, 110 (2013), pp. 233901/1233901/5.
Abstract
We demonstrate a novel method for supercontinuum generation in an optical fiber based on twocolor pumping with a delay and a group velocity matching. The scheme relies on the enhanced crossphasemodulation at an intensity induced refractive index barrier between a dispersive wave and a soliton. The generation mechanism neither incorporates soliton fission nor a modulation instability and therefore exhibits extraordinary coherence properties, enabling the temporal compression of octave bandwidth into a short pulse. Moreover, the properties of the supercontinuum are adjustable over a wide range in the frequency domain by suitable choice of the dispersive wave. 
A. Demircan, S. Amiranashvili, C. Brée, F. Mitschke, G. Steinmeyer, From optical rogue waves to optical transistors, Nonlinear Phenomena in Complex Systems, 16 (2013), pp. 2432.
Abstract
We study the propagation of fewcycle optical solitons in nonlinear media with an anomalous, but otherwise arbitrary, dispersion and a cubic nonlinearity. Our approach does not derive from the slowly varying envelope approximation. The optical field is derived directly from Maxwell's equations under the assumption that generation of the third harmonic is a nonresonant process or at least cannot destroy the pulse prior to inevitable linear damping. The solitary wave solutions are obtained numerically up to nearly singlecycle duration using the spectral renormalization method originally developed for the envelope solitons. The theory explicitly distinguishes contributions between the essential physical effects such as higherorder dispersion, selfsteepening, and backscattering, as well as quantifies their influence on ultrashort optical solitons. 
A. Demircan, S. Amiranashvili, C. Brée, Ch. Mahnke, F. Mitschke, G. Steinmeyer, Rogue wave formation by accelerated solitons at an optical event horizon, Applied Physics B: Lasers and Optics, 115 (2013), pp. 343354.
Abstract
Rogue waves, by definition, are rare events of extreme amplitude, but at the same time they are frequent in the sense that they can exist in a wide range of physical contexts. While many mechanisms have been demonstrated to explain the appearance of rogue waves in various specific systems, there is no known generic mechanism or general set of criteria shown to rule their appearance. Presupposing only the existence of a nonlinear Schrödingertype equation together with a concave dispersion profile around a zero dispersion wavelength we demonstrate that solitons may experience acceleration and strong reshaping due to the interaction with continuum radiation, giving rise to extremevalue phenomena. The mechanism is independent of the optical Raman effect. A strong increase of the peak power is accompanied by a mild increase of the pulse energy and carrier frequency, whereas the photon number of the soliton remains practically constant. This reshaping mechanism is particularly robust and is naturally given in optics in the supercontinuum generation process. 
U. Bandelow, N. Akhmediev, Solitons on a background, rogue waves and classical soliton solutions of SasaSatsuma equation, Journal of Optics, 15 (2013), pp. 064006/1064006/10.
Abstract
We present the most general multiparameter family of a soliton on a background solutions to the SasaSatsuma equation. The solution contains a set of several free parameters that control the background amplitude as well as the soliton itself. This family of solutions admits nontrivial limiting cases, such as rogue waves and classical solitons, that are considered in detail. 
C. Brée, S. Amiranashvili, U. Bandelow, Spatiotemporal pulse propagation in nonlinear dispersive optical media, Optical and Quantum Electronics, 45 (2013), pp. 727733.
Abstract
We discuss stateofart approaches to modeling of propagation of ultrashort optical pulses in one and three spatial dimensions.We operate with the analytic signal formulation for the electric field rather than using the slowly varying envelope approximation, because the latter becomes questionable for fewcycle pulses. Suitable propagation models are naturally derived in terms of unidirectional approximation. 
S. Amiranashvili, U. Bandelow, A. Mielke, Calculation of ultrashort pulse propagation based on rational approximations for medium dispersion, Optical and Quantum Electronics, 44 (2012), pp. 241246.
Abstract
Ultrashort optical pulses contain only a fewoptical cycles and exhibit broad spectra. Their carrier frequency is therefore not well defined and their description in terms of the standard slowly varying envelope approximation becomes questionable. Existing modeling approaches can be divided in two classes, namely generalized envelope equations, that stem from the nonlinear Schrödinger equation, and nonenvelope equations which treat the field directly. Based on fundamental physical rules we will present an approach that effectively interpolates between these classes and provides a suitable setting for accurate and highly efficient 
V. Tronciu, S. Schwertfeger, M. Radziunas, A. Klehr, U. Bandelow, H. Wenzel, Numerical simulation of the amplification of picosecond laser pulses in tapered semiconductor amplifiers and comparison with experimental results, Optics Communications, 285 (2012), pp. 28972904.
Abstract
We apply a travelling wave model to the simulation of the amplification of laser pulses generated by Qswitched or modelocked distributedBragg reflector lasers. The power amplifier monolithically integrates a ridgewaveguide section acting as preamplifier and a flared gainregion amplifier. The diffraction limited and spectralnarrow band pulses injected in to the preamplifier have durations between 10 ps and 100 ps and a peak power of typical 1 W. After the amplifier, the pulses reach a peak power of several tens of Watts preserving the spatial, spectral and temporal properties of the input pulse. We report results obtained by a numerical solution of the travellingwave equations and compare them with experimental investigations. The peak powers obtained experimentally are in good agreement with the theoretical predictions. The performance of the power amplifier is evaluated by considering the dependence of the pulse energy as a function of different device and material parameters. 
U. Bandelow, N. Akhmediev, Persistence of rogue waves in extended nonlinear Schrödinger equations: Integrable SasaSatsuma case, Physics Letters A, 376 (2012), pp. 15581561.
Abstract
We present the lowest order rogue wave solution of the SasaSatsuma equation (SSE) which is one of the integrable extensions of the nonlinear Schrödinger equation (NLSE). In contrast to the Peregrine solution of the NLSE, it is significantly more involved and contains polynomials of fourth order rather than second order in the corresponding expressions. The correct limiting case of Peregrine solution appears when the extension parameter of the SSE is reduced to zero. 
U. Bandelow, N. Akhmediev, SasaSatsuma equation: Soliton on a background and its limiting cases, Phys. Rev. E (3), 86 (2012), pp. 026606/1026606/8.
Abstract
We present a multiparameter family of a soliton on a background solutions to the SasaSatsuma equation. The solution is controlled by a set of several free parameters that control the background amplitude as well as the soliton itself. This family of solutions admits a few nontrivial limiting cases that are considered in detail. Among these special cases is the NLSE limit and the limit of rogue wave solutions. 
C. Brée, S. Amiranashvili, U. Bandelow, Spatiotemporal pulse propagation in nonlinear dispersive optical media, Optical and Quantum Electronics, (2012), pp. 012963/1012963/7.
Abstract
We discuss stateofart approaches to modeling of propagation of ultrashort optical pulses in one and three spatial dimensions.We operate with the analytic signal formulation for the electric field rather than using the slowly varying envelope approximation, because the latter becomes questionable for fewcycle pulses. Suitable propagation models are naturally derived in terms of unidirectional approximation. 
C. Brée, A. Demircan, G. Steinmeyer, KramersKronig relations and high order nonlinear susceptibilities, Physical Review A, 85 (2012), pp. 033806/1033806/8.
Abstract
As previous theoretical results recently revealed, a KramersKronig transform of multiphoton absorption rates allows for a precise prediction on the dispersion of the nonlinear refractive index $n_2$ in the near IR. It was shown that this method allows to reproduce recent experimental results on the importance of the higherorder Kerr effect. Extending these results, the current manuscript provides the dispersion of $n_2$ for all noble gases in excellent agreement with reference data. It is furthermore established that the saturation and inversion of the nonlinear refractive index is highly dispersive with wavelength, which indicates the existence of different filamentation regimes. While shorter laser wavelengths favor the wellestablished plasma clamping regime, the influence of the higherorder Kerr effect dominates in the long wavelength regime. 
S. Amiranashvili, A. Demircan, Ultrashort optical pulse propagation in terms of analytic signal, Advances in Optical Technologies, (2011), pp. 989515/1989515/8.
Abstract
We demonstrate that ultrashort optical pulses propagating in a nonlinear dispersive medium are naturally decribed through incorporation of analytic signal for the electric field. To this end a secondorder nonlinear wave equation is first simplified using an unidirectional approximation. Then the analytic signal is introduced and all nonresonant nonlinear terms are eliminated. The derived prpagation equation accounts for arbitrary dispersion, resonant fourwave mixing processes, weak absorption, and arbitrary pulse duration. The model applies to the complex electric field and is independent of the slowly varying envelopeapproximation. Still the derived propagation equation universal structure of the generalized nonlinear Srödinger equation (NSE). in particular, it can be solved numerically with only small changes of the standard splitstep solver or more complicted spectral algorithms for NSE. we present exemplary numerical solutions describing supercontimuum generation with an ultrashort optical pulse. 
S. Amiranashvili, U. Bandelow, N. Akhmediev, Dispersion of nonlinear group velocity determines shortest envelope solitons, Physical Review A, 84 (2011), pp. 043834/1043834/5.
Abstract
We demonstrate that a generalized nonlinear Schrödinger equation (NSE), that includes dispersion of the intensitydependent group velocity, allows for exact solitary solutions. In the limit of a long pulse duration, these solutions naturally converge to a fundamental soliton of the standard NSE. In particular, the peak pulse intensity times squared pulse duration is constant. For short durations this scaling gets violated and a cusp of the envelope may be formed. The limiting singular solution determines then the shortest possible pulse duration and the largest possible peak power. We obtain these parameters explicitly in terms of the parameters of the generalized NSE. 
C. Brée, A. Demircan, J. Bethge, E.T.J. Nibbering, S. Skupin, L. Bergé, G. Steinmeyer, Filamentary pulse selfcompression: The impact of the cell windows, Physical Review A, 83 (2011), pp. 043803/1043803/7.
Abstract
Selfcompression of multimillijoule laser pulses during filamentary propagation is usually explained by the interplay of selffocusing and defocusing effects, causing a substantial concentration of energy on the axis of the propagating optical pulse. Recently, it has been argued that cell windows may play a decisive role in the selfcompression mechanism. As such windows have to be used for media other than air their presence is often unavoidable, yet they present a sudden nonadiabatic change in dispersion and nonlinearity that should lead to a destruction of the temporal and spatial integrity of the light bullets generated in the selfcompression mechanism. We now experimentally prove that there is in fact a selfhealing mechanism that helps to overcome the potentially destructive consequences of the cell windows. We show in two carefully conducted experiments that the cell window position decisively influences activation or inhibition of the selfhealing mechanism. A comparison with a windowless cell shows that presence of this mechanism is an important prerequisite for the exploitation of selfcompression effects in windowed cells filled with inert gases. 
A.G. Vladimirov, R. Lefever, M. Tlidi, Relative stability of multipeak localized patterns of cavity solitons, Physical Review A, 84 (2011), pp. 043848/1043848/4.
Abstract
We study the relative stability of different onedimensional (1D) and twodimensional (2D) clusters of closely packed localized peaks of the SwiftHohenberg equation. In the 1D case, we demonstrate numerically the existence of a spatial Maxwell transition point where all clusters involving up to 15 peaks are equally stable. Above (below) this point, clusters become more (less) stable when their number of peaks increases. In the 2D case, since clusters involving more than two peaks may exhibit distinct spatial arrangements, this point splits into a set of Maxwell transition pointsWe study the relative stability of different onedimensional (1D) and twodimensional (2D) clusters of closely packed localized peaks of the SwiftHohenberg equation. In the 1D case, we demonstrate numerically the existence of a spatial Maxwell transition point where all clusters involving up to 15 peaks are equally stable. Above (below) this point, clusters become more (less) stable when their number of peaks increases. In the 2D case, since clusters involving more than two peaks may exhibit distinct spatial arrangements, this point splits into a set of Maxwell transition points 
I. Babushkin, S. Skupin, A. Husakou, Ch. Köhler, E. CabreraGranado, L. Bergé, J. Herrmann, Tailoring terahertz radiation by controlling tunnel photoionization events in gases, New Journal of Physics, 13 (2011), pp. 123029/1123029/16.
Abstract
Applications ranging from nonlinear terahertz spectroscopy to remote sensing require broadband and intense THz radiation which can be generated by focusing twocolor laser pulses into a gas. In this setup, THz radiation originates from the buildup of the electron density in sharp steps of attosecond duration due to tunnel ionization, and subsequent acceleration of free electrons in the laser field. We show that the spectral shape of the THz pulses generated by this mechanism is determined by superposition of contributions from individual ionization events. This provides a straightforward analogy with linear diffraction theory, where the ionization events play the role of slits in a grating. This analogy offers simple explanations for recent experimental observations and opens new avenues for THz pulse shaping based on temporal control of the ionization events. We illustrate this novel technique by tailoring the spectral width and position of the resulting radiation using multicolor pump pulses. 
J. Bethge, G. Steinmeyer, G. Stibenz, P. Staudt, C. Brée, A. Demircan, H. Redlin, S. Düsterer , Selfcompression of 120 fs pulses in a whitelight filament, Journal of Optics, 13 (2011), pp. 055203/1055203/7.
Abstract
Selfcompression of pulses with >100 fs input pulse duration from a 10 Hz laser system is experimentally demonstrated, with a compression factor of 3.3 resulting in output pulse durations of 35 fs. This measurement substantially widens the range of applicability of this compression method, enabling selfcompression of pulsed laser sources that neither exhibit extremely low pulsetopulse energy fluctuations nor a particularly clean beam profile. The experimental demonstration is numerically modeled, revealing the exact same mechanisms at work as at shorter input pulse duration. Additionally, the role of controlled beam clipping with an adjustable aperture is numerically substantiated. 
A. Demircan, S. Amiranashvili, G. Steinmeyer, Controlling light by light with an optical event horizon, Physical Review Letters, 108 (2011), pp. 163901/1163901/4.
Abstract
A novel concept for an alloptical transistor is proposed and verified numerically. This concept relies on crossphase modulation between a signal and a control pulse. Other than previous approaches, the interaction length is extended by temporally locking control and signal pulse in an optical event horizon, enabling continuous modification of central wavelength, energy, and duration of a signal pulse by an up to sevenfold weaker control pulse. Moreover, if the signal pulse is a soliton it may maintain its solitonic properties during the switching process. The proposed alloptical switching concept fulfills all criteria for a useful optical transistor in [Nature Photon. 4, 3 (2010)], in particular, fanout and cascadability, which have previously proven as most difficult to meet. 
CH. Köhler, E. CabreraGranado, I. Babushkin, L. Bergé, J. Herrmann, S. Skupin, Directionality of terahertz emission from photoinduced gas plasmas, Optics Letters, 36 (2011), pp. 31663168.
Abstract
Forward and backward THz emission by ionizing twocolor laser pulses in gas is investigated by means of a simple semianalytical model based on Jefimenko's equation and rigorous Maxwell simulations in one and two dimensions. We find the emission in backward direction having a much smaller spectral bandwidth than in forward direction and explain this by interference effects. Forward THz radiation is generated predominantly at the ionization front and is thus almost not affected by the opacity of the plasma, in excellent agreement with results obtained from a unidirectional pulse propagation model. 
C. Brée, A. Demircan, G. Steinmeyer, Modulation instability in filamentary selfcompression, Laser Physics, 21 (2011), pp. 13131318.
Abstract
We numerically analyze filamentary propagation for various medium and input pulse parameters and show that temporal selfcompression can greatly benefit from refocusing events. Analyzing the dynamical behavior in the second focal spot, it turns out that a dispersive temporal breakup may appear due to the emission of a hyperbolic shockwave from the selfsteepened trailing edge of the pulse. This breakup event enhances the selfcompression capabilities of laser filaments, enabling up to 12fold temporal compression. Only slightly perturbing the input pulse parameters, we further identify a regime in which refocusing events give rise to extended subdiffractive propagation in a weakly ionized channel. 
S. Amiranashvili, A. Demircan, Hamiltonian structure of propagation equations for ultrashort optical pulses, Physical Review A, 82 (2010), pp. 013812/1013812/11.

S. Amiranashvili, A.G. Vladimirov, U. Bandelow, A model equation for ultrashort optical pulses around the zero dispersion frequency, The European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics, 58 (2010), pp. 219226.
Abstract
The nonlinear Schrödinger equation based on the Taylor approximation of the material dispersion can become invalid for ultrashort and fewcycle optical pulses. Instead, we use a rational fit to the dispersion function such that the resonances are naturally accounted for. This approach allows us to derive a simple nonenvelope model for short pulses propagating in one spatial dimension. This model is further investigated numerically and analytically. 
S. Amiranashvili, U. Bandelow, A. Mielke, Padé approximant for refractive index and nonlocal envelope equations, Optics Communications, 283 (2010), pp. 480485.
Abstract
Padé approximant is superior to Taylor expansion when functions contain poles. This is especially important for response functions in complex frequency domain, where singularities are present and intimately related to resonances and absorption. Therefore we introduce a diagonal Padé approximant for the complex refractive index and apply it to the description of short optical pulses. This yields a new nonlocal envelope equation for pulse propagation. The model offers a global representation of arbitrary medium dispersion and absorption, e.g., the fulfillment of the KramersKronig relation can be established. In practice, the model yields an adequate description of spectrally broad pulses for which the polynomial dispersion operator diverges and can induce huge errors. 
C. Brée, A. Demircan, G. Steinmeyer, Method for computing the nonlinear refractive index via Keldysh theory, IEEE J. Quantum Electron., 46 (2010), pp. 433437.

C. Brée, J. Bethge, S. Skupin, L. Bergé, A. Demircan, G. Steinmeyer, Cascaded selfcompression of femtosecond pulses in filaments, New Journal of Physics, 12 (2010), pp. 093046/1093046/11.

C. Brée, A. Demircan, S. Skupin, L. Bergé, G. Steinmeyer, Plasma induced pulse breaking in filamentary selfcompression, Laser Physics, 20 (2010), pp. 11071113.
Abstract
A plasma induced temporal breakup in filamentary propagation has recently been identified as one of the key events in the temporal selfcompression of femtosecond laser pulses. An analysis of the Nonlinear Schrödinger Equation coupled to a noninstantaneous plasma response yields a set of stationary states. This analysis clearly indicates that the emergence of doublehump, characteristically asymmetric temporal onaxis intensity profiles in regimes where plasma defocusing saturates the optical collapse caused by Kerr selffocusing is an inherent property of the underlying dynamical model. 
A.G. Vladimirov, U. Bandelow, G. Fiol, D. Arsenijević, M. Kleinert, D. Bimberg, A. Pimenov, D. Rachinskii, Dynamical regimes in a monolithic passively modelocked quantum dot laser, Journal of the Optical Society of America. B, 27 (2010), pp. 21022109.

J. Becker, K. Gärtner, R. Klanner, R. Richter, Simulation and experimental study of plasma effects in planar silicon sensors, Nuclear Instruments and Methods in Physics Research Section A, 624 (2010), pp. 716727.

J. Bethge, G. Steinmeyer, G. Stibenz, P. Staudt, C. Brée, A. Demircan, H. Redlin, S. Düsterer , Selfcompression of 120 fs pulses in a whitelight filament, Journal of Optics, 13 (2011), pp. 055203/1055203/7.
Abstract
Selfcompression of pulses with >100 fs input pulse duration from a 10 Hz laser system is experimentally demonstrated, with a compression factor of 3.3 resulting in output pulse durations of 35 fs. This measurement substantially widens the range of applicability of this compression method, enabling selfcompression of pulsed laser sources that neither exhibit extremely low pulsetopulse energy fluctuations nor a particularly clean beam profile. The experimental demonstration is numerically modeled, revealing the exact same mechanisms at work as at shorter input pulse duration. Additionally, the role of controlled beam clipping with an adjustable aperture is numerically substantiated. 
H.G. Purwins, H. Bödeker, S. Amiranashvili, Dissipative solitons, Advances in Physics, 59 (2010), pp. 485701.

M. Tlidi, A.G. Vladimirov, D. Turaev, G. Kozyreff, D. Pieroux, T. Erneux, Spontaneous motion of localized structures and localized patterns induced by delayed feedback, The European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics, 59 (2010), pp. 5965.

I. Babushkin, W. Kuehn, Ch. Köhler, S. Skupin, L. Bergé, K. Reimann, M. Woerner, J. Herrmann, Th. Elsaesser, Ultrafast spatiotemporal dynamics of terahertz generation by ionizing twocolor femtosecond pulses in gases, Physical Review Letters, 105 (2010), pp. 053903/1053903/4.
Abstract
We present a combined theoretical and experimental study of spatiotemporal propagation effects in terahertz (THz) generation in gases using twocolor ionizing laser pulses. The observed strong broadening of the THz spectra with increasing gas pressure reveals the prominent role of spatiotemporal reshaping and of a plasmainduced blueshift of the pump pulses in the generation process. Results obtained from (3+1)dimensional simulations are in good agreement with experimental findings and clarify the mechanisms responsible for THz emission. 
I. Babushkin, S. Skupin, J. Herrmann, Generation of terahertz radiation from ionizing twocolor laser pulses in Ar filled metallic hollow waveguides, Optics Express, 18 (2010), pp. 96589663.
Abstract
The generation of THz radiation from ionizing twocolor femtosecond pulses propagating in metallic hollow waveguides filled with Ar is numerically studied. We observe a strong reshaping of the lowfrequency part of the spectrum. Namely, after several millimeters of propagation the spectrum is extended from hundreds of GHz up to $sim 150$ THz. For longer propagation distances, nearly singlecycle nearinfrared pulses with wavelengths around 4.5 $mu$m are obtained by appropriate spectral filtering, with an efficiency of up to 0.25 %. 
S. Amiranashvili, U. Bandelow, A. Mielke, Padé approximant for refractive index and nonlocal envelope equations, Optics Communications, 283 (2009), pp. 480485.
Abstract
Padé approximant is superior to Taylor expansion when functions contain poles. This is especially important for response functions in complex frequency domain, where singularities are present and intimately related to resonances and absorption. Therefore we introduce a diagonal Padé approximant for the complex refractive index and apply it to the description of short optical pulses. This yields a new nonlocal envelope equation for pulse propagation. The model offers a global representation of arbitrary medium dispersion and absorption, e.g., the fulfillment of the KramersKronig relation can be established. In practice, the model yields an adequate description of spectrally broad pulses for which the polynomial dispersion operator diverges and can induce huge errors. 
C. Brée, A. Demircan, S. Skupin, L. Bergé, G. Steinmeyer, Selfpinching of pulsed laser beams during filamentary propagation, Optics Express, 17 (2009), pp. 1642916435.

C. Brée, A. Demircan, G. Steinmeyer, Asymptotic pulse shapes in filamentary propagation of intense femtosecond pulses, Laser Physics, 19 (2009), pp. 330335.

G. Kozyreff, M. Tlidi, A. Mussot, E. Louvergneaux, M. Taki, A.G. Vladimirov, Localized beating between dynamically generated frequencies, Physical Review Letters, 102 (2009), pp. 043905/1043905/4.

M. Tlidi, A.G. Vladimirov, D. Pieroux, D. Turaev, Spontaneous motion of cavity solitons induced by a delayed feedback, Physical Review Letters, 103 (2009), pp. 103904/1103904/4.

S. Amiranashvili, A.G. Vladimirov, U. Bandelow, Solitarywave solutions for fewcycle optical pulses, Physical Review A, 77 (2008), pp. 063821/1063821/7.

M. Pietrzyk, I. Kanattšikow, U. Bandelow, On the propagation of vector ultrashort pulses, Journal of Nonlinear Mathematical Physics, 15 (2008), pp. 162170.

A. Bhattacherjee, M. Pietrzyk, Transport behaviour of a BoseEinstein condensate in a bichromatic optical lattice, Central European Journal of Mathematics, 6 (2008), pp. 2632.
Abstract
The Bloch and dipole oscillations of a Bose Einstein condensate (BEC) in an optical superlattice is investigated. We show that the effective mass increases in an optical superlattice, which leads to localization of the BEC, in accordance with recent experimental observations [17]. In addition, we find that the secondary optical lattice is a useful additional tool to manipulate the dynamics of the atoms. 
D. Turaev, M. Radziunas, A.G. Vladimirov, Chaotic soliton walk in periodically modulated media, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 77 (2008), pp. 06520/106520/4.

A. Demircan, M. Pietrzyk, U. Bandelow, Effects of higherorder dispersion on pulse splitting in the normal dispersion regime, Optical and Quantum Electronics, 40 (2008), pp. 455460.

M. Tlidi, A. Mussot, E. Louvergneaux, G. Kozyreff, A.G. Vladimirov, M. Taki, Control and removing of modulational instabilities in low dispersion photonic crystal fiber cavities, Optics Letters, 32 (2007), pp. 662664.

D. Turaev, A.G. Vladimirov, S. Zelik, Chaotic bound state of localized structures in the complex GinzburgLandau equation, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 75 (2007), pp. 045601/1045601/4.

A. Demircan, U. Bandelow, Analysis of the interplay between soliton fission and modulation instability in supercontinuum generation, Applied Physics B: Lasers and Optics, 86 (2007), pp. 3139.

A.G. Vladimirov, D.V. Skryabin, G. Kozyreff, P. Mandel, M. Tlidi, Bragg localized structures in a passive cavity with transverse modulation of the refractive index and the pump, Optics Express, 14 (2006), pp. 16.

M. Nizette, D. Rachinskii, A. Vladimirov, M. Wolfrum, Pulse interaction via gain and loss dynamics in passive modelocking, Physica D. Nonlinear Phenomena, 218 (2006), pp. 95104.

A. Yulin, D. Skryabin, A.G. Vladimirov, Modulation instability of discrete solitons in coupled waveguides with group velocity dispersion, Optics Express, 14 (2006), pp. 1234712352.

A. Demircan, M. Kroh, U. Bandelow, B. Hüttl, H.G. Weber, Compression limit by thirdorder dispersion in the normal dispersion regime, IEEE Phot. Tech. Letter, 18 (2006), pp. 23532355.

A. Demircan, U. Bandelow, Limit for pulse compression by pulse splitting, Optical and Quantum Electronics, 38 (2006), pp. 11671172.

A. Demircan, U. Bandelow, Supercontinuum generation by the modulation instability, Optics Communications, 244 (2005), pp. 181185.

S.V. Fedorov, N.N. Rosanov, A.N. Shatsev, N.A. Veretenov, A.G. Vladimirov, Topologically multicharged and multihumped rotating solitons in wideaperture lasers with saturable absorber, IEEE J. Quantum Electron., 39 (2003), pp. 216226.

N. Seehafer, A. Demircan, Dynamo action in cellular convection, Magnetohydrodynamics. Consultants Bureau, New York (US). Consultants Bureau, New York. Translation from: Magnitnaya Gidrodinamika., 39 (2003), pp. 335342.

M. Tlidi, A.G. Vladimirov, P. Mandel, Interaction and stability of periodic and localized structures in optical bistable systems, IEEE J. Quantum Electron., 39 (2003), pp. 197205.
Contributions to Collected Editions

G. Slavcheva, M.V. Koleva, A. Pimenov, Simulation of nonlinear polariton dynamics in microcavity wires for polaritonic integrated circuits, in: Proceedings of ,,Numerical Simulation of Optoelectronic Devices (NUSOD), 2017 International Conference on'', IEEE, New York, 2017, DOI 10.1109/NUSOD.2017.8010054 .

D. Puzyrev, A.G. Vladimirov, A. Pimenov, S.V. Gurevich, S. Yanchuk, Pulse boundstate clusters in coupled modelocked lasers, in: Lasers and ElectroOptics Europe & European Quantum Electronics Conference (CLEO/EuropeEQEC), IEEE, New York, 2017, DOI 10.1109/CLEOEEQEC.2017.8087527 .
Abstract
Modelocked semiconductor lasers are widely used for generation of short optical pulses with high repetition rates and optical frequency combs suitable for numerous practical applications. By combining many lasers into an array one can achieve much larger output power and substantially improve the characteristics of the output radiation. In this presentation we study dynamical regimes of operation in an array of modelocked lasers locally coupled in a ring geometry. We demonstrate that unlike a solitary modelocked laser emitting a sequence of equidistant pulses with the pulse repetition frequency close to the inverse cavity round trip time, an array of modelocked lasers can radiate a periodic sequence of clusters of fundamental modelocked pulses. This regime associated with the formation of closely packed bound states of coupled modelocked pulses due to a balance between attraction and repulsion is very different from the standard harmonic modelocked regime where the pulses always repel each other. 
S. Pickartz, U. Bandelow, S. Amiranashvili, Cancellation of Raman selffrequency shift for compression of optical pulses, in: Proceedings of ``the 17th International Conference on Numerical Simulation of Optoelectronic Devices'', J. Piprek, M. Piprek, eds., IEEE Conference Publications Management Group, Piscataway, 2017, pp. 173174.

M. Kretschmar, C. Brée, T. Nagy, H. Kurz, U. Morgner, M. Kovacev, Highorder harmonics as a nonlinear tool to track pulsedynamics along a filament, in: HighBrightness Sources and LightDriven Interactions, OSA Technical Digest (Online), Optical Society of America, Washington, DC, 2016, pp. HS4B.5/1HS4B.5/3.
Abstract
We report on the direct observation of pulse dynamics along a filament and its connection to directly emitted highorder harmonic radiation, whose nonlinear nature is used to gain further insight into the filamentary propagation dynamics. 
G. Steinmeyer, S. Birkholz, C. Brée, A. Demircan, Nonlinear time series analysis: Towards an effective forecast of rogue waves, in: Realtime Measurements, Rogue Events, and Emerging Applications, B. Jalali, S.K. Turitsyn, D.R. Solli, J.M. Dudley, eds., 9732 of Proceedings of SPIE, Society of PhotoOptical Instrumentation Engineers (SPIE), 2016, pp. 973205/1973205/6.
Abstract
Rogue waves are extremely large waves that exceed any expectation based on longterm observation and Gaussian statistics. Ocean rogue waves exceed the significant wave height in the ocean by a factor 2. Similar phenomena have been observed in a multiplicity of optical systems. While the optical systems show a much higher frequency of rogue events than the ocean, it appears nevertheless questionable what conclusions can be drawn for the prediction of ocean rogue waves. Here we tackle the problem from a different perspective and analyze the predictability of rogue events in two optical systems as well as in the ocean using nonlinear timeseries analysis. Our analysis is exclusively based on experimental data. The results appear rather surprising as the optical rogue wave scenario of fiberbased supercontinuum generation does not allow any prediction whereas real ocean rogue waves and a multifilament scenario do bear a considerable amount of determinism, which allows, at least in principle, the prediction of extreme events. It becomes further clear that there exist two fundamentally different types of roguewave supporting systems. One class of rogue waves is obviously seeded by quantum fluctuations whereas in the other class, linear random interference of waves seems to prevail. 
S. Pickartz, U. Bandelow, S. Amiranashvili, Numerical optimization of alloptical switching, in: Proceedings of the 16th International Conference on Numerical Simulation of Optoelectronic Devices, J. Piprek, Ch. Poulton, M. Steel, M. DE Sterke, eds., IEEE Conference Publications Management Group, Piscataway, 2016, pp. 189190.
Abstract
A possibility to control an optical soliton by a much weaker second pulse that is scattered on the soliton attracted considerable attention recently. An important problem here is to quantify the small range of parameters at which the interaction takes place. This has been achieved by using adiabatic ODEs for the soliton characteristics, which is much faster than a scan of the full propagation equations for all parameters in question. 
C. Brée, I. Babushkin, U. Morgner, A. Demircan, Collapse regularization of filaments by resonant radiation, in: Conference on Lasers and ElectroOptics, OSA Technical Digest (online), Optical Society of America, Washington, DC, 2016, pp. JW2A.60/1JW2A.60/2.
Abstract
We show that the transfer of optical power via emission of resonant radiation plays an important role for regularizing the optical collapse enabling stable filament propagation of highpower nearinfrared pulses in bulk silica. 
M. Tlidi, E. Averlant, A.G. Vladimirov, A. Pimenov, S. Gurevich, K. Panayotov, Localized structures in broad area VCSELs: Experiments and delayinduced motion, in: Structural Nonlinear Dynamics and Diagnosis, M. Belhaq, ed., 168 of Springer Proceedings in Physics, Springer, 2015, pp. 329349/1329349/21.

U. Bandelow, S. Amiranashvili, N. Akhmediev, Limitation for ultrashort solitons in nonlinear optical fibers by cusp formation, in: CLEO®/Europe  EQEC 2015: Conference Digest, OSA Technical Digest (Online) (Optical Society of America, 2015), paper EI2.3 THU, 2015, pp. 11.

S. Amiranashvili, U. Bandelow, N. Akhmediev, Recent progress in theory of pulse propagation in optical fibers, in: Proceedings of the 14th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD 2014, 14 September 2014, J. Piprek, J. Javaloyes, eds., IEEE Conference Publications Management Group, Piscataway, NJ, USA, 2014, pp. 131132.

R.M. Arkhipov, M.V. Arkhipov, Modelocking in two section and single section lasers due to coherent interaction of light and matter in the gain and absorbing media, in: Proceedings of the XIV School Seminar Wave Phenomena in Inhomogeneous Media (Waves 2014), Section 3, Nonlinear and coherent optics (in electronic form and in Russian), 2014, pp. 4345.

S. Amiranashvili, A. Demircan, C. Brée, G. Steinmeyer, F. Mitschke, Manipulating light by light in optical fibers, in: 3rd Bonn Humboldt Award Winners' Forum ``Frontiers in Quantum Optics: Taming the World of Atoms and Photons  100 Years after Niels Bohr'', Bonn, October 912, 2013, Networking Guide, pp. 5859.

A.G. Vladimirov, D. Rachinskii, M. Wolfrum, Modeling of passively modelocked semiconductor lasers, in: Nonlinear Laser Dynamics: From Quantum Dots to Cryptography, K. Lüdge, ed., Reviews in Nonlinear Dynamics and Complexity, WILEYVCH Verlag GmbH & Co. KGaA, Weinheim, 2012, pp. 183216.

I. Babushkin, S. Skupin, C. Köhler, L. Bergé, J. Herrmann, Modeling of THz emission from plasmagenerating femtosecond laser pulses with unidirectional Maxwell equation in plasma spots and in guided geometries, in: Book of Abstracts of the 2nd International Workshop on LaserMatter Interaction 2010, September 1317, 2010, Porquerolles, France, 2010, pp. 49.

C. Brée, J. Bethge, A. Demircan, E.T. Nibbering, G. Steinmeyer, On the origin of negative dispersion contributions in filamentary propagation, in: Conference on Lasers and ElectroOptics (CLEO), OSA Technical Digest (CD), Optical Society of America, 2010, pp. CMU2/1CMU2/2.
Abstract
http://www.opticsinfobase.org/abstract.cfm?URI=CLEO2010CMU2 
C. Brée, J. Bethge, S. Skupin, L. Bergé, A. Demircan, G. Steinmeyer, Double selfcompression of femtosecond pulses in filaments, in: Conference on Lasers and ElectroOptics (CLEO), OSA Technical Digest (CD), Optical Society of America, 2010, pp. JThD6/1JThD6/2.

A.G. Vladimirov, M. Wolfrum, G. Fiol, D. Arsenijević, D. Bimberg, E. Viktorov, P. Mandel, D. Rachinskii, Locking characteristics of a 40GHz hybrid modelocked monolithic quantum dot laser, in: Semiconductor Lasers and Laser Dynamics IV, K. Panajotov, M. Sciamanna, A.A. Valle, R. Michalzik, eds., 7720 of Proceedings of SPIE, SPIE, 2010, pp. 77200Y/177200Y/8.

C. Brée, A. Demircan, S. Skupin, L. Bergé, G. Steinmeyer, Nonlinear photon zpinching in filamentary selfcompression, in: Conference on Lasers and ElectroOptics/International Quantum Electronics Conference, OSA Technical Digest (CD), Optical Society of America, 2009, pp. ITuC1/1ITuC1/2.

C. Brée, A. Demircan, S. Skupin, L. Bergé, G. Steinmeyer, Nonlinear photon zpinching in filamentary selfcompression, in: CLEO/Europe and EQEC 2009 Conference Digest (Optical Society of America, 2009), paper CF5_4, 2009, pp. 11.

C. Krüger, A. Demircan, S. Skupin, G. Stibenz, N. Zhavoronkov, G. Steinmeyer, Asymptotic pulse shapes and pulse selfcompression in femtosecond filaments, in: Ultrafast Phenomena XVI, Proceedings of the 16th International Conference, June 913, 2009, Stresa, Italy, P. Corkum, S. Silvestri, K.A. Nelson, E. Riedle, R.W. Schoenlein, eds., 92 of Springer Series in Chemical Physics, Springer, 2009, pp. 804.

D. Turaev, A.G. Vladimirov, S. Zelik, Strong enhancement of interaction of optical pulses induced by oscillatory instability, in: CLEO/Europe and EQEC 2009 Conference Digest (Optical Society of America, 2009), poster EH.P.13 WED, 2009, pp. 11.

C. Krüger, A. Demircan, G. Stibenz, N. Zhavoronkov, G. Steinmeyer, Asymptotic pulse shapes in filamentary propagation of femtosecond pulses and selfcompression, in: Conference on Lasers and ElectroOptics/Quantum Electronics and Laser Science Conference, May 0409, 2008, San Jose, CA, 19 of IEEE Lasers and ElectroOptics Society (LEOS) Annual Meeting, IEEE, New York, NY, USA, 2008, pp. 25012502.

M. Pietrzyk, I. Kanattšikow, A. Demircan, On the compression of ultrashort optical pulses beyond the slowly varying envelope approximation, in: Proceedings of the 8th International Conference on Numerical Simulation of Optoelectronic Devices NUSOD'08, J. Piprek, E. Larkins, eds., IEEE/LEOS, 2008, pp. 5960.

A. Mussot, M. Tlidi, E. Louvergneaux, G. Kozyref, A.G. Vladimirov, M. Taki, Removing modulational instabilities in low dispersion fiber cavities, in: 2007 European Conference on Lasers and ElectroOptics and the European Quantum Electronics Conference (CLEO® / EuropeIQEC) Conference Digest (oral presentation CD9WED), IEEE, 2007, pp. 11.

T. Ziems, K.N. Adarsh, M. Böhm, A. Demircan, F.M. Mitschke, Selforganized supercontinuum generation from a nonlinear fiber resonator, in: Bragg Gratings, Photosensitivity, and Poling in Glass Waveguides, OSA Technical Digest (CD), 2007, pp. JWBPDP7/1JWBPDP7/3.

A. Demircan, M. Kroh, M. Pietrzyk, B. Hüttl, U. Bandelow, NonRaman redshift by pulse splitting in the normal dispersion regime, in: Proceedings of the 7th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD '07, 2427 September 2007, J. Piprek, D. Prather, eds., IEEE, Piscataway, NJ, 2007, pp. 99100.

A. Demircan, U. Bandelow, M. Kroh, B. Hüttl, Generation of new frequencies by pulse splitting, in: Proceedings of ECOC 07, 5, VDE Verlag GmbH, Berlin/Offenbach, 2007, pp. 7374.

A. Demircan, U. Bandelow, Interplay between soliton fission and modulation instability, in: Proceedings of the European Conference on Lasers and ElectroOptics, 2007, and the International Quantum Electronics Conference. CLEO/IQEC 2007 (oral presentation CF3MON), IEEE, 2007, pp. 11.

A.G. Vladimirov, D.V. Skryabin, M. Tlidi, Localized structures of light in nonlinear devices with intracavity photonic bandgap material, in: 2007 European Conference on Lasers and ElectroOptics and the European Quantum Electronics Conference (CLEO®/EuropeIQEC) Conference Digest (oral presentation IG4MON), IEEE, 2007, pp. 11.

U. Bandelow, A. Demircan, Pulse splitting by thirdorder dispersion, in: Proc. of the 6th Int. Conf. on Numerical Simulation of Optoelectronic Devices (NUSOD 06) IEEE Catalog 06EX1456, J. Piprek, S.F. Yu, eds., IEEE, Piscataway, NJ, 2006, pp. 113114.

U. Bandelow, A. Demircan, Impact of modulation instability on the supercontinuum generation, in: Proceedings of the 5th International Conference on ``Numerical Simulation of Optoelectronic Devices'' (NUSOD'05) in Berlin, September 1922, 2005, H.J. Wünsche, J. Piprek, U. Bandelow, H. Wenzel, eds., IEEE, Piscataway, NJ, 2005, pp. 6566.
Preprints, Reports, Technical Reports

S. Amiranashvili, M. Radziunas, U. Bandelow, R. Čiegis, Numerical methods for accurate description of ultrashort pulses in optical fibers, Preprint no. 2470, WIAS, Berlin, 2018, DOI 10.20347/WIAS.PREPRINT.2470 .
Abstract, PDF (2140 kByte)
We consider a onedimensional firstorder nonlinear wave equation (the socalled forward Maxwell equation, FME) that applies to a fewcycle optical pulse propagating along a preferred direction in a nonlinear medium, e.g., ultrashort pulses in nonlinear fibers. The model is a good approximation to the standard secondorder wave equation under assumption of weak nonlinearity. We compare FME to the commonly accepted generalized nonlinear Schrödinger equation, which quantifies the envelope of a quickly oscillating wave field based on the slowly varying envelope approximation. In our numerical example, we demonstrate that FME, in contrast to the envelope model, reveals new spectral lines when applied to fewcycle pulses. We analyze and compare pseudospectral numerical schemes employing symmetric splitting for both models. Finally, we adopt these schemes to a parallel computation and discuss scalability of the parallelization. 
C. Brée, M. Hofmann, I. Babushkin, A. Demircan, U. Morgner, O.G. Kosareva, A.B. Savel'ev, A. Husakou, M. Ivanov, Symmetry breaking and strong persistent plasma currents via resonant destabilization of atoms, Preprint no. 2423, WIAS, Berlin, 2017, DOI 10.20347/WIAS.PREPRINT.2423 .
Abstract, PDF (1839 kByte)
The ionization rate of an atom in a strong optical field can be resonantly enhanced by the presence of longliving atomic levels (so called Freeman resonances). This process is most prominent in the multiphoton ionization regime meaning that ionization event takes many optical cycles. Nevertheless, here we show that these resonances can lead to fast subcyclescale plasma buildup at the resonant values of the intensity in the pump pulse. The fast buildup can break the cycletocycle symmetry of the ionization process, resulting in generation of persistent macroscopic plasma currents which remain after the end of the pulse. This, in turn, gibes rise to a broadband radiation of unusual spectral structure forming a comb from terahertz (THz) to visible. This radiation contains fingerprints of the attosecond electronic dynamics in Rydberg states during ionization. 
S. Pickartz, C. Brée, U. Bandelow, S. Amiranashvili, Cancellation of Raman selffrequency shift for compression of optical pulses, Preprint no. 2419, WIAS, Berlin, 2017, DOI 10.20347/WIAS.PREPRINT.2419 .
Abstract, PDF (3334 kByte)
We study to which extent a fiber soliton can be manipulated by a specially chosen continuous pump wave. A group velocity matched pump scatters at the soliton, which is compressed due to the energy/momentum transfer. As the pump scattering is very sensitive to the velocity matching condition, soliton compression is quickly destroyed by the soliton selffrequency shift (SSFS). This is especially true for ultrashort pulses: SSFS inevitably impairs the degree of compression. We demonstrate numerically that soliton enhancement can be restored to some extent and the compressed soliton can be stabilized, provided that SSFS is canceled by a second pump wave. Still the available compression degree is considerably smaller than that in the Ramanfree nonlinear fibers. 
G. Slavcheva, M.V. Koleva, A. Pimenov, The impact of microcavity wire width on polariton soliton existence and multistability, Preprint no. 2381, WIAS, Berlin, 2017, DOI 10.20347/WIAS.PREPRINT.2381 .
Abstract, PDF (5652 kByte)
We have developed a model of the nonlinear polariton dynamics in realistic 3D nonplanar microcavity wires in the drivendissipative regime [15]. We find that the typical microcavity optical bistability evolves into multistability upon variation of the model parameters. The origin of the multistability is discussed in detail. We apply linear perturbation analysis to modulational instabilities, and identify conditions for localisation of composite multimode polariton solitons in the triggered parametric oscillator regime. Further, we demonstrate stable polariton soliton propagation in tilted and tapered waveguides, and determine maximum tilt angles for which solitons are still found. Additionally, we study soliton amplitude and velocity dependence on the wire width, with a view towards device applications. 
D. AnguloGarcia, S. Luccioli, S. Olmi, A. Torcini, Neurons' death and rebirth in sparse heterogeneous inhibitory networks, Preprint no. 2306, WIAS, Berlin, 2016.
Abstract, PDF (6118 kByte)
Inhibition is a key aspect of neural dynamics playing a fundamental role for the emergence of neural rhythms and the implementation of various information coding strategies. Inhibitory populations are present in several brain structures and the comprehension of their dynamics is strategical for the understanding of neural processing. In this paper, we discuss a general mechanism present in pulsecoupled heterogeneous inhibitory networks: inhibition can induce not only suppression of the neural activity, as expected, but it can also promote neural reactivation. In particular, for globally coupled systems, the number of firing neurons monotonically reduces upon increasing the strength of inhibition (neurons? death). The introduction of a sparse connectivity in the network is able to reverse the action of inhibition, i.e. a sufficiently strong synaptic strength can surprisingly promote, rather than depress, the activity of the neurons (neurons? rebirth). Specifically, for small synaptic strengths, one observes an asynchronous activity of nearly independent suprathreshold neurons. By increasing the inhibition, a transition occurs towards a regime where the neurons are all effectively subthreshold and their irregular firing is driven by current fluctuations. We explain this transition from a meandriven to a fluctuationdriven regime by deriving an analytic mean field approach able to provide the fraction of active neurons together with the first two moments of the firing time distribution. We show that, by varying the synaptic time scale, the mechanism underlying the reported phenomenon remains unchanged. However, for sufficiently slow synapses the effect becomes dramatic. For small synaptic coupling the fraction of active neurons is frozen over long times and their firing activity is perfectly regular. For larger inhibition the active neurons display an irregular bursting behaviour induced by the emergence of correlations in the current fluctuations. In this latter regime the model gives predictions consistent with experimental findings for a specific class of neurons, namely the medium spiny neurons in the striatum. 
S. Olmi, A. Torcini, Chimera states in pulse coupled neural networks: The influence of dilution and noise, Preprint no. 2305, WIAS, Berlin, 2016.
Abstract, PDF (706 kByte)
We analyse the possible dynamical states emerging for two symmetrically pulse coupled populations of leaky integrateandfire neurons. In particular, we observe broken symmetry states in this setup: namely, breathing chimeras, where one population is fully synchronized and the other is in a state of partial synchronization (PS) as well as generalized chimera states, where both populations are in PS, but with different levels of synchronization. Symmetric macroscopic states are also present, ranging from quasiperiodic motions, to collective chaos, from splay states to population antiphase partial synchronization. We then investigate the influence disorder, random link removal or noise, on the dynamics of collective solutions in this model. As a result, we observe that broken symmetry chimeralike states, with both populations partially synchronized, persist up to 80% of broken links and up to noise amplitudes ' 8% of thresholdreset distance. Furthermore, the introduction of disorder on symmetric chaotic state has a constructive effect, namely to induce the emergence of chimeralike states at intermediate dilution or noise level. 1 Introduction 
M. Hofmann, C. Brée, Adiabatic Floquet model for the optical response in femtosecond filaments, Preprint no. 2217, WIAS, Berlin, 2016.
Abstract, PDF (398 kByte)
The standard model of femtosecond filamentation is based on phenomenological assumptions which suggest that the ionizationinduced carriers can be treated as free according to the Drude model, while the nonlinear response of the bound carriers follows the alloptical Kerr effect. Here, we demonstrate that the additional plasma generated at a multiphoton resonance dominates the saturation of the nonlinear refractive index. Since resonances are not captured by the standard model, we propose a modification of the latter in which ionization enhancements can be accounted for by an ionization rate obtained from nonHermitian Floquet theory. In the adiabatic regime of long pulse envelopes, this augmented standard model is in excellent agreement with direct quantum mechanical simulations. Since our proposal maintains the structure of the standard model, it can be easily incorporated into existing codes of filament simulation.
Talks, Poster

S. Amiranashvili, Negative frequency radiation in optical fibers, Institutskolloquium, WIAS, Berlin, October 16, 2017.

C. Brée, Bloch mode transfer matrix method for photonic crystals, Internal seminar of the research group DONLL, Universitat Politecnica de Catalunya, Terrassa, Spain, July 12, 2017.

A. Pimenov, Novel delayed model of a broadarea laser: Are the light bullets robust?, Minisymposium ,,Dynamics of novel modelocked and frequencyswept lasers (DNMFL2017)'', December 18  19, 2017, WIAS, Berlin, December 18, 2017.

A. Pimenov, Temporal localized structures in a time delay model of a ring laser, International Workshop: Nonlinear Waves and Turbulence in Optics and Hydrodynamics, WIAS, Berlin, March 23, 2017.

U. Bandelow, Applied mathematical research in photonics at WIAS, BoschWIAS Workshop, WIAS, Berlin, June 13, 2017.

U. Bandelow, Fewcycle solitons that do not want to be too short in duration, CLEO Pacific Rim Conference, July 31  August 4, 2017, The Optical Society, Singapore, Singapore, August 2, 2017.

U. Bandelow, Models for ultrashort optical pulses and their limiting soliton solutions, International Workshop: Nonlinear Waves and Turbulence in Optics and Hydrodynamics, WIAS, Berlin, March 22, 2017.

C. Brée, Detection of dynamic resonances in femtosecond filaments via the transient plasma grating effect, Workshop ,,Nonlinear phenomena in strong fields'', Leibniz Universität Hannover, January 25, 2017.

S. Amiranashvili, Extreme solitons in optical fibers, Workshop on Abnormal Wave Events, University of Nice Sophia Antipolis, Nice, France, June 15, 2016.

S. Amiranashvili, How to become a champion soliton, International Conference on Wave Interaction (WIN2016), Johannes Kepler Universität Linz, Austria, April 27, 2016.

S. Pickartz, S. Amiranashvili, Champion solitons that come from nowhere, 618. WEHeraeusSeminar: Extreme Events and Rogue Waves  2016, Wilhelm und Else HeraeusStiftung, Bad Honnef, May 30  June 3, 2016.

S. Pickartz, U. Bandelow, S. Amiranashvili, Numerical optimization of alloptical switching, 16th International Conference on Numerical Simulation of Optoelectronic Devices, Sydney, Australia, July 11  15, 2016.

U. Bandelow, Heteroclinic connections and limiting cases in integrable NLStype equations, 618. WEHeraeusSeminar: Extreme Events and Rogue Waves  2016, Wilhelm und Else HeraeusStiftung, Bad Honnef, June 3, 2016.

U. Bandelow, Multidimensional modeling and simulation of electrically pumped semiconductorbased emitters, Block Seminar GraalMüritz, DFG Collaborative Research Center (SFB) 787 ``Semiconductor Nanophotonics'', GraalMüritz, May 13, 2016.

U. Bandelow, Solitons on a background, rogue waves, and classical soliton solutions of extended nonlinear Schrödinger equations, International Tandem Workshop on Pattern Dynamics in Nonlinear Optical Cavities, August 15  19, 2016, MaxPlanckInstitut für Physik komplexer Systeme, Dresden, August 15, 2016.

U. Bandelow, Solitons that do not want to be too short in duration, International Conference on Wave Interaction (WIN2016), Johannes Kepler Universität Linz, Austria, April 27, 2016.

U. Bandelow, Ultrashort solitons, rogue waves and event horizons in nonlinear dispersive optical media, Coloquio de la Faculdad de Ingenieria y Ciencias Aplicadas, Universidad de los Andes, Santiago, Chile, December 15, 2016.

C. Brée, Adiabatic Floquet model for the optical response in subpicosecond optical filamentation, III International Symposium ``Advances in Nonlinear Photonics'' (ANPh'2016), September 29  October 1, 2016, Belarusian State University, Minsk, Belarus, September 30, 2016.

A.G. Vladimirov, Interaction of temporal cavity solitons in driven fiber resonators and modelocked lasers, International Tandem Workshop on Pattern Dynamics in Nonlinear Optical Cavities, August 15  19, 2016, MaxPlanckInstitut für Physik komplexer Systeme, Dresden, August 15, 2016.

A.G. Vladimirov, Nonlinear dynamics of a frequency swept laser, Quantum Optics Seminar, SaintPetersburg State University, SaintPetersburg, Russian Federation, January 12, 2016.

M. Hofmann, C. Brée, On the role of Freeman resonances in pumpprobe measurements of the nonlinear refractive index, CLEO/EuropeEQEC 2015 Conference, München, June 19  25, 2015.

M. Hofmann, Abinitio description of optical nonlinearities in femtosecond filaments, International Workshop ``Waves, Solitons and Turbulence in Optical Systems'' (WASTOS15), Berlin, October 12  14, 2015.

M. Hofmann, Intensity clamping at a Freeman resonance, CLEO: 2015  Laser Science to Photonic Applications, May 9  19, 2015, San José, USA, May 11, 2015.

M. Hofmann, Intensity clamping at a Freeman resonance, CLEO/EuropeEQEC 2015 Conference, June 19  25, 2015, München, June 22, 2015.

M. Hofmann, Nonlinear refractive index in filaments governed by resonantly enhanced ionization, 24th Annual International Laser Physics Workshop (LPHYS'15), August 21  25, 2015, Shanghai, China.

M. Hofmann, Numerical solution of the time dependent Schrödinger equation, Seminar Week, LeibnizUniversität Hannover, Institut für Quantenoptik, Ultrafast Laser Laboratory, Dahnsdorf, October 7, 2015.

M. Hofmann, Saturation of the nonlinear refractive index due to resonantly enhanced ionization, Internationaler Workshop ``Nonlinear Photonics: Theory, Materials, Applications'', June 29  July 2, 2015, St. Petersburg, Russian Federation, July 2, 2015.

D. Puzyrev, Delay induced multistability and wiggling movement of laser cavity solitons, International Workshop ``Waves, Solitons and Turbulence in Optical Systems'' (WASTOS15), Berlin, October 12  14, 2015.

D. Puzyrev, Instabilities of laser cavity solitons induced by delayed feedback, CLEO/EuropeEQEC 2015 Conference, München, June 21  25, 2015.

D. Puzyrev, Multistability and bifurcations of laser cavity solitons induced by delayed feedback, International Workshop ``Nonlinear Photonics: Theory, Materials, Applications'', Session ``Laser Dynamics'', June 29  July 2, 2015, SaintPetersburg State University, Departmetnt of General Physics, Russian Federation, July 1, 2015.

D. Puzyrev, Multistability and bifurcationsof laser cavity solitons induced by delayed feedback, Workshop on Control of SelfOrganizing Nonlinear Systems, September 14  16, 2015, SFB 910 ``Control of selforganizing nonlinear systems: Theoretical methods and concepts of application'', Lutherstadt Wittenberg, September 15, 2015.

S. Pickartz, Scattering of dispersive waves by optical solitons, International Workshop: Waves, Solitons and Turbulence in Optical Systems (WASTOS15), WeierstraßInstitut für Angewandte Analysis und Stochastik, Berlin, October 14, 2015.

U. Bandelow, Limitation for ultrashort solitons in nonlinear optical fibers by cusp formation, CLEO/EuropeEQEC 2015 Conference, June 21  25, 2015, München, June 25, 2015.

C. Brée, A model of intense lasermatter interaction based on complexrotated Floquet resonances, 24th Annual International Laser Physics Workshop (LPHYS'15), Seminar 5: Nonlinear Optics & Spectroscopy, August 21  25, 2015, Shanghai, China, August 23, 2015.

C. Brée, Impact of resonanceenhanced ionization on femtosecond filamentation, International Workshop ``Nonlinear Photonics: Theory, Materials, Applications'', Session: Extreme and Relativistic Nonlinear Optics, June 28  July 4, 2015, St. Petersburg State University, St . Petersburg, Russian Federation, July 2, 2015.

C. Brée, Numerical modelling of femtosecond filamentation, LeibnizUniversität Hannover, Institut für Quantenoptik, Hannover, September 7, 2015.

O. Omel'chenko, Chimera states for any taste, Dynamics of Coupled Oscillators: 40 Years of the Kuramoto Mode, July 27  31, 2015, Max Planck Institute for the Physics of Complex Systems, Dresden, July 27, 2015.

O. Omel'chenko, Controlling unstable chaos in systems of coupled oscillators, The 8th International Conference on Chaotic Modeling, Simulation and Applications (CHAOS2015), Minisymposium ``Emergent Dynamics and Control'', May 25  30, 2015, Institut Henri Poincaré, Paris, France, May 28, 2015.

S. Amiranashvili, Elementary processes behind turbulent states in optical fibers, Weak Chaos and Weak Turbulence, February 3  7, 2014, MaxPlanckInstitut für Physik komplexer Systeme, Dresden, February 5, 2014.

S. Amiranashvili, Extreme waves in optical fibers, Wave Interaction (WIN2014), April 23  26, 2014, Johannes Kepler University, Linz, Austria, April 24, 2014.

S. Amiranashvili, Recent progress in theory of pulse propagation in optical fibers, 14th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD 2014), September 1  5, 2014, Palma de Mallorca, Spain, September 2, 2014.

S. Amiranashvili, Solitons who do not want to be too short, Workshop on Abnormal Wave Events (WAWE2014), June 5  6, 2014, Nice, France, June 5, 2014.

M. Hofmann, Intense lasermatter interaction in atomic gases and crystalline solids, LeibnizUniversität Hannover, Institut für Quantenoptik, February 27, 2014.

M. Hofmann, On the transient optical response of atomic gases, Frühjahrstagung der Deutschen Physikalischen Gesellschaft (DPG), March 17  21, 2014, HumboldtUniversität zu Berlin, Berlin.

C. Brée, M. Kretschmar, T. Nagy, M. Hofmann, A. Demircan, U. Morgner, M. Kovacev, Fingerprint of selfcompression in the high harmonic spectrum from a filament, HighIntensity Lasers and HighField Phenomena (HILAS), Berlin, March 18  20, 2014.

C. Brée, Manipulating optical solitons with a groupvelocity horizon, Vortrag und Junior Researcher im Rahmen des Rank Prize Fund Symposiums, June 16  19, 2014, Grasmere, UK, June 18, 2014.

A.G. Vladimirov, Delay differential equations in laser dynamics, International ConferenceSchool Hamiltonian Dynamics, Nonautonomous Systems, and Patterns in PDE's, December 10  15, 2014, Nishni Novgorod, Russian Federation, December 14, 2014.

S. Amiranashvili, Mathematics and physics behind short pulses in optical fibers, Habilitandenkolloquium, HumboldtUniversität zu Berlin, Institut für Physik, February 5, 2013.

S. Amiranashvili, Solitons that are too short in duration, International Workshop: Extreme Nonlinear Optics & Solitons, October 28  30, 13, WIAS Berlin, October 28, 2013.

U. Bandelow, Propagation of ultrashort pulses in nonlinear dispersive optical media: Solitons, rogue waves and horizons, Technische Universität Wien, Institut für Theoretische Physik, Austria, June 4, 2013.

S. Amiranashvili, A modeling framework for short pulses in optical fibers, 5th Annual Meeting ``Photonic Devices'', ZuseInstitut Berlin (ZIB), Berlin, February 24, 2012.

S. Amiranashvili, Mathematics and physics behind short pulses in optical fibers, Optik / PhotonikKolloquium, Humboldt Universität zu Berlin, November 8, 2012.

S. Amiranashvili, Tiny waves we should never ignore, OSA  The Optical Society, Topical Meeting ``Nonlinear Photonics'', June 17  21, 2012, Colorado Springs, USA, June 18, 2012.

C. Brée, Saturation of the alloptical Kerr effekt, LPHYS'11, 20th International Laser Physics Workshop Sarajevo, Bosnia and Herzegowina, July 1115 2011, Bosnia And Herzegovina, July 13, 2011.

S. Amiranashvili, Can dispersive radiation feed energy into a giant wave?, Rogue Waves, November 7  11, 2011, Dresden, November 9, 2011.

S. Amiranashvili, Manipulating light by light, XXXth URSI General Assembly and Scientific Symposium of International Union of Radio Science, August 13  20, 2011, Istanbul, Turkey, August 18, 2011.

S. Amiranashvili, Optical transistor: From optical event horizons to rogue waves, Rogue Waves, Dresden, November 7  11, 2011.

U. Bandelow, Calculation of ultrashort pulse propagation based on rational approximations for dispersion, 11th Intl. Conference on Numerical Simulation of Optoelectronic Devices NUSOD'11, Rom, Italy, September 8, 2011.

I. Babushkin, Modeling of THz emission from plasmagenerating femtosecond laser pulses with unidirectional Maxwell equation in plasma spots and in guided geometries, 2nd International Workshop on LaserMatter Interaction 2010, September 1317, 2010, Porquerolles, France, September 17, 2010, September 13, 2010.

A. Demircan, Plasma induced pulse breakup in filamentary selfcompression, Laser Optics Berlin, March 22  24, 2010, March 24, 2010.

A.G. Vladimirov, Introduction to modelocking in lasers, Graduate College of the Collaborative Research Center SFB 787 ``Semiconductor Nanophotonics: Materials, Models, Devices'', May 9  11, 2010, Technische Universität Berlin, Institut für Festkörperphysik, GraalMüritz, May 10, 2010.

A.G. Vladimirov, Localized structures of light and their interaction, Imperial College London, Department of Applied Mathematics, UK, April 27, 2010.

A.G. Vladimirov, Nonlinear dynamics in lasers, Technische Universität Berlin, Institut für Festkörperphysik, March 24, 2010.

S. Amiranashvili, Modeling of short optical pulses, Localized Structures in Dissipative Nonlinear Systems, October 18  20, 2010, WIAS, October 19, 2010.

S. Amiranashvili, Modeling of medium dispersion for ultrashort optical pulses, WIAS Workshop ``Nonlinear Optics in Guided Geometries'', May 18  20, 2009, WIAS, Berlin, May 18, 2009.

S. Amiranashvili, Modeling of ultrashort optical pulses, Workshop ``Pulses and Modulations in Nonlinear Systems'', February 25  27, 2009, Universität Stuttgart, February 26, 2009.

C. Brée, A. Demircan, S. Skupin, L. Bergé, G. Steinmeyer, Quasihydrodynamic spatiotemporal shaping in filamentary propagation of femtosecond pulses, 73th Annual Meeting of the DPG and DPG Spring Meeting of the Section AMOP, March 1  6, 2009, Universität Hamburg, March 2, 2009.

C. Brée, A. Demircan, S. Skupin, G. Steinmeyer, Nonlinear photon zpinching in filamentary selfcompression, European Conference on Lasers and ElectroOptics and the XIth European Quantum Electronics Conference (CLEO®/EuropeEQEC 2009), June 15  19, 2009, Munich, June 18, 2009.

C. Brée, Quasihydrodynamic spatiotemporal shaping in filamentary propagation of femtosecond pulses, WIAS Workshop ``Nonlinear Optics in Guided Geometries'', May 18  20, 2009, WIAS, Berlin, May 20, 2009.

A.G. Vladimirov, Enhancement of interaction of dissipative solitons above selfpulsing instability threshold, CPNLW09 Soliton 2009 ``Solitons in Their Roaring Forties: Coherence and Persistence in Nonlinear Waves'', January 6  9, 2009, Nice University, Nice, France, January 8, 2009.

A.G. Vladimirov, Spontaneous motion of dissipative solitons under the effect of delay, Australasian Conference on Optics, Lasers and Spectroscopy and Australian Conference on Optical Fibre Technology in association with the International Workshop on Dissipative Solitons (ACOLS ACOFT DS 2009), November 29  December 3, 2009, University of Adelaide, Australia, December 1, 2009.

A.G. Vladimirov, Strong enhancement of interaction of optical pulses induced by oscillatory instability, European Conference on Lasers and ElectroOptics and the XIth European Quantum Electronics Conference 2009 (CLEOtextsuperscript®/Europe  EQEC 2009, Munich, June 14  19, 2009.

I. Babushkin, S. Skupin, J. Herrmann, Generation of tunable ultrabroad supercontinuum from THz to nearinfrared in twocolor ultrashort pulses in hollow capillaries, IOP Conference ``Nonlinear Photonics in Micro and Nanostructures'', London, UK, December 10, 2009.

I. Babushkin, Nonresonant frequency conversion with ultrashort intense pulses in hollow microcapillaries, University of Bath, Department of Physics, UK, December 9, 2009.

I. Babushkin, Optical amplification by fourwave mixing in gases using quasiphasematching with ultrasound waves, Workshop ``Nonlinear Optics in Guided Geometries'', May 18  20, 2009, WIAS, Berlin, May 20, 2009.

U. Bandelow, Mathematical models for ultrashort optical pulses, Australasian Conference on Optics, Lasers and Spectroscopy and Australian Conference on Optical Fibre Technology in association with the International Workshop on Dissipative Solitons (ACOLS ACOFT DS 2009), November 29  December 3, 2009, University of Adelaide, Australia, November 30, 2009.

U. Bandelow, Nonlinear and nonlocal models for ultrashort optical pulses, Fourth `Rio de la Plata' Workshop on Laser Dynamics and Nonlinear Photonics, December 8  11, 2009, Piriapolis, Uruguay, December 9, 2009.

U. Bandelow, Solitary wave solutions for fewcycle optical pulses, WIAS Workshop ``Nonlinear Optics in Guided Geometries'', May 18  20, 2009, WIAS, Berlin, May 19, 2009.

C. Krüger, A. Demircan, G. Stibenz, N. Zhavoronkov, G. Steinmeyer, Asymptotic pulse shapes and pulse selfcompression in femtosecond filaments, UP 2008: XVI Conference on Ultrafast Phenomena, Stresa, Italy, June 9  13, 2008.

C. Krüger, A. Demircan, G. Stibenz, N. Zhavoronkov, G. Steinmeyer, Asymptotic pulse shapes in filamentary propagation of femtosecond pulses and selfcompression, CLEO/QUELS 2008: Conference on Lasers and ElectroOptics/Quantum Electronics and Laser Science Conference, San Jose, USA, May 4  9, 2008.

C. Krüger, Asymptotic pulse shapes in filamentary propagation of femtosecond pulses, MaxPlanckInstitut für Physik komplexer Systeme, Dresden, March 31, 2008.

C. Krüger, Asymptotic pulse shapes in filamentary propagation of ultrashort laser pulses, MaxBornInstitut Berlin, June 19, 2008.

C. Krüger, Selbstkompression und asymptotische Pulsformen in Filamenten, DPGFrühjahrstagung 2008, March 10  14, 2008, Darmstadt, March 13, 2008.

M. Pietrzyk, I. Kanattšikow, Multisymplectic integrators in nonlinear optics, PHOTON08: Conference in Optics and Photonics, Edinburgh, UK, August 26  29, 2008.

M. Pietrzyk, Carrierwave shock formation and other properties of the short pulse equation, PHOTON08: Conference in Optics and Photonics, August 26  29, 2008, UK Consortium for Photonics and Optics (UKCPO), Edinburgh, UK, August 29, 2008.

M. Pietrzyk, On the compression of ultrashort optical pulses beyond the slowly varying envelope approximation, 8th International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) 2008, September 1  5, 2008, University of Nottingham, UK, September 2, 2008.

M. Pietrzyk, On the multisymplectic integrator for the generalized short pulse equation, 40th Symposium on Mathematical Physics ``Geometry & Quanta'', June 25  28, 2008, Nicolaus Copernicus University, Toruń, Poland, June 28, 2008.

M. Pietrzyk, Short pulse equations and its properties, Gdańsk University of Technology, Department of Theoretical Physics and Quantum Information, Poland, July 1, 2008.

M. Pietrzyk, The short pulse equation: Fewcycle optical pulses beyond the slowly varying envelope approximation, University of Tartu, Institute of Physics, Estonia, October 8, 2008.

A.G. Vladimirov, Nonlinear dynamics of pulse interactions in bistable optical systems, V International Conference ``Basic Problems of Optics'' BPO2008 in the framework of V International Congress ``Optics  XXI century'', October 20  24, 2008, St Petersburg, Russian Federation, October 23, 2008.

U. Bandelow, Short pulses in nonlinear optical fibers: Models and applications, Colloquium ``Nonlinear Dynamics in Complex Optical Systems'', HumboldtUniversität zu Berlin, Institut für Physik, June 19, 2008.

U. Bandelow, Solitary wave solutions for ultrashort optical pulses, Technical Conference ``Frontiers in Optics 2008, Laser Science XXIV'', October 19  23, 2008, Optical Society of America (OSA), Rochester, USA, October 21, 2008.

I. Kanattšikow, The short pulse equation: Integrability and generalizations, Gdańsk University of Technology, Institute of Theoretical Physics and Quantum Informatics, Gdańsk, Poland, June 30, 2008.

M. Pietrzyk, How to describe ultrashort pulses when the NSE does not apply?, University of Vigo, Optics Lab, Spain, July 2, 2007.

M. Pietrzyk, Multisymplectic analysis of the short pulse equation, 10th International Conference on Differential Geometry and Its Application, August 27  31, 2007, Olomouc, Czech Republic, August 28, 2007.

M. Pietrzyk, Properties of ultrashort pulses in silica fibers, ATTO 07  International Workshop and 391th WWEHeraeus Seminar Attosecond Physics, Dresden, July 31  August 4, 2007.

U. Bandelow, A. Demircan, M. Kroh, B. Hüttl, Appearance of solitonic effects during pulse compression in the normal dispersion regime, Rio de la Plata Workshop on Noise, Chaos and Complexity in Lasers and Nonlinear Optics, Punta del Este, Uruguay, December 3  6, 2007.

U. Bandelow, Limit for pulse compression by pulse splitting, Workshop ``Nonlinear Effects in Photonic Materials'', March 12  14, 2007, WIAS, Berlin, March 13, 2007.

U. Bandelow, Nichtlineare Effekte in Halbleiterlasern und optischen Fasern, Habilitandenkolloquium, HumboldtUniversität zu Berlin, Institut für Physik, April 17, 2007.

U. Bandelow, NonRaman redshift by pulse splitting, 7th International Conference ``Numerical Simulation of Optoelectronic Devices'' (NUSOD'07), September 24  27, 2007, University of Delaware, Newark, USA, September 27, 2007.

A. Demircan, U. Bandelow, B. Hüttl, M. Kroh, Generation of new frequencies by pulse splitting, 33rd European Conference and Exhibition on Optical Communication (ECOC 2007), Berlin, September 16  20, 2007.

A. Demircan, U. Bandelow, Interplay between soliton fission and modulation instability, European Conference on Lasers and ElectroOptics 2007/International Quantum Electronics Conference (CLEOEIQEC 2007), München, June 17  22, 2007.

A. Demircan, Interplay between soliton fission and modulation instability, Workshop ``Nonlinear Effects in Photonic Materials'', March 12  14, 2007, WIAS, Berlin, March 14, 2007.

A. Vladimirov, Autosolitons in optical devices with transverse refractive index modulation, International Conference on Coherent and Nonlinear Optics/International Conference on Lasers, Applications, and Technologies (ICONO/LAT 2007), May 28  June 1, 2007, Minsk, Belarus, May 29, 2007.

A. Vladimirov, Dissipative solitons in nonlinear optical devices with refractive index modulation, Workshop ``Nonlinear Effects in Photonic Materials'', March 12  14, 2007, WIAS, Berlin, March 14, 2007.

A. Demircan, U. Bandelow, Compression limit by thirdorder dispersion in the normal dispersion regime, 14th European Conference on Mathematics for Industry (ECMI 2006), Universidad Carlos III de Madrid, Spain, July 10  14, 2006.

A. Demircan, Analysis of the interplay between soliton fission and modulational instability in supercontinuum generation, Minisymposium on Dissipative Solitons, WIAS, Berlin, April 20, 2006.

A. Demircan, Compression limit by thirdorder dispersion, FraunhoferInstitut für Nachrichtentechnik, HeinrichHertzInstitut, Berlin, January 10, 2006.

A. Demircan, Interplay between soliton fission and modulation instability in the supercontinuum generation, University of Bath, Centre for Photonics and Photonic Materials, UK, August 21, 2006.

M. Pietrzyk, Ultrashort pulses beyond the slowlyvarying envelope approximation, Workshop ``Nonlinear Dynamics in Modelocked Lasers and Optical Fibers'', July 13  14, 2006, WIAS, Berlin, July 14, 2006.

U. Bandelow, A. Demircan, A. Mielke, M. Pietrzyk, Nonlocal and nonlinear effects in fiber optics, Evaluation Colloquium of the DFG Research Center sc Matheon, Berlin, January 24  25, 2006.

U. Bandelow, Limitations for pulse compression, Workshop "Nonlinear Dynamics in Modelocked Lasers and Optical Fibers", July 13  14, 2006, WIAS, Berlin, July 14, 2006.

U. Bandelow, Modellierung und Simulation von Pulsquellen, Status Seminar TerabitOptics Berlin, HeinrichHertzInstitut für Nachrichtentechnik, Berlin, July 4, 2006.

U. Bandelow, Pulse compression limit in the normal dispersion regime, The 90th OSA Annual Meeting 'Frontiers in Optics', October 8  12, 2006, Rochester, USA, October 12, 2006.

U. Bandelow, Pulse splitting by thirdorder dispersion, 6th Intl. Conference on Numerical Simulation of Optoelectronic Devices NUSOD'06, September 11  14, 2006, Nanyang University, Singapore, September 14, 2006.

A. Vladimirov, Dynamics of light pulses in modelocked lasers, 6th Crimean School and Workshops ``Nonlinear Dynamics, Chaos and Applications'', May 15  26, 2006, Yalta, Crimea, Ukraine, May 20, 2006.

A. Vladimirov, Laser dissipative solitons and their interaction, Minisymposium on Dissipative Solitons, WIAS, Berlin, April 20, 2006.

A. Vladimirov, Localized structures of light in laser systems and their weak interactions, Technische Universität Berlin, June 14, 2006.

A. Vladimirov, Nonlinear dynamics and bifurcations in multimode and spatially distributed laser systems, June 20  23, 2006, St. Petersburg State University, Russian Federation, June 20, 2006.

A. Vladimirov, Nonlinear dynamics in multimode and spatially extended laser systems, Moscow State University, Physics Faculty, Russian Federation, November 10, 2006.

A. Vladimirov, Transverse Bragg dissipative solitons in a Kerr cavity with refractive index modulation, Laser Optics Conference, June 26  30, 2006, St. Petersburg, Russian Federation, June 28, 2006.

A. Demircan, U. Bandelow, Impact of modulation instability on supercontinuum generation, Annual Meeting 2005 of the Optical Society of America (OSA) ``Frontiers in Optics'', October 17  21, 2005, Tuscon, USA, October 19, 2005.

A. Demircan, Supercontinuum generation by the modulation instability, WIAS Workshop ``Nonlinear Dynamics in Photonics'', May 2  4, 2005, Berlin, May 3, 2005.

A. Vladimirov, G. Kozyreff, P. Mandel, M. Tlidi, Localized structures in a passive cavity with refractive index modulation, International Quantum Electronics Conference, June 12  17, 2005, München, June 15, 2005.

A. Vladimirov, Interaction of dissipative solitons in laser systems, Ben Gurion University of the Negev, Department of Mathematics, Beer Sheva, Israel, November 17, 2005.

D. Turaev, S. Zelik, A. Vladimirov, Chaotic bound state of localized structures in the complex GinzburgLandau equation, Conference Digest ``Nonlinear Guided Waves and their Applications'', Dresden, September 6  9, 2005.

U. Bandelow, A. Demircan, Impact of the modulation instability on supercontinuum generation, Conference on Lasers and ElectroOptics/Quantum Electronics & Lasers Science Conference CLEO/QELS 2005, München, June 12  17, 2005.

U. Bandelow, A. Demircan, Impact of modulation instability on the supercontinuum generation, 5th International Conference ``Numerical Simulation of Optoelectronic Devices'' (NUSOD'05), September 19  22, 2005, HumboldtUniversität zu Berlin, September 21, 2005.

U. Bandelow, Modellierung und Simulation von Pulsquellen, Status Seminar of the TerabitOpticsBerlin Project, Fraunhofer Institut für Nachrichtentechnik, HeinrichHertzInstitut, Berlin, May 31, 2005.

U. Bandelow, A. Demircan, M. Kesting, Pulse propagation in nonlinear optical fibers, Meeting within the TerabitOpticsBerlin Project, FraunhoferInstitut für Nachrichtentechnik, HeinrichHertzInstitut, Berlin, April 28, 2004.

U. Bandelow, Modellierung und Simulation von Pulsquellen, Status Seminar of the TerabitOpticsBerlin Project, Technische Universität Berlin, May 3, 2004.

U. Bandelow, Modellierung und Simulation von Pulsquellen, Status Seminar of the TerabitOpticsBerlin Project, Technische Universität Berlin, November 2, 2004.

U. Bandelow, Report on WIAS activities concerning COST Action 288, Kickoff Meeting for the Cost Action 288, COST TIST Secretariat, Brussels, Belgium, April 7, 2003.

A. Demircan, Generation of ultrabroad spectra in optical fibers, WIAS Workshop ``Dynamics of Semiconductor Lasers'', September 15  17, 2003, Berlin, September 17, 2003.

A. Vladimirov, Moving discrete solitons in multicore fibers and waveguide arrays, European Quantum Electronics Conference, June 22  27, 2003, München, June 25, 2003.

A. Vladimirov, Moving discrete solitons in multicore fibers and waveguide arrays, Conference dedicated to the 60th birthday of Prof. Paul Mandel, April 11  12, 2003, Université Libre de Bruxelles, Optique Nonlinéaire Théorique, Belgium, April 11, 161613.
External Preprints

J. Becker, K. Gärtner, R. Klanner, R. Richter, Simulation and experimental study of plasma effects in planar silicon sensors, Preprint no. arXiv:1007.4433, Cornell University Library, arXiv.org, 2010.

S. Amiranashvili, U. Bandelow, A.G. Vladimirov, Solitary wave solutions for fewcycle optical pulses, Preprint no. 500, DFG Research Center sc Matheon, 2008.