Nonlinear Dynamics in Semiconductor Lasers - Abstract

Grillot, Frederic

Quantum cascade lasers with external feedback

Quantum cascade lasers (QCLs) are unipolar semiconductor lasers based on intersubband transitions within the conduction band [1]. Mid-infrared (IR) QCLs can now operate in single- or multimode configuration, in pulsed or continuous-wave operation, at room temperature with thermo-electrical cooling, and have therefore become privileged sources for gas spectroscopy, free-space communications or optical countermeasures. QCLs are renowned for their high stability compared to interband laser diodes, in particular when subjected to external phenomena such as optical feedback [2]. In laser diodes, optical feedback, ie. reinjection of part of the emitted light after reflection on a mirror, can destabilize the laser and may lead to a chaotic behavior [3]. On the other hand, no chaos has been observed so far in mid-IR QCLs, even though experimental studies have shown that optical feedback can influence static properties such as laser threshold, output power or wavelength [4]. The analysis of the optical spectra of a distributed feedback (DFB) QCL in several feedback conditions furthermore evidences a set of feedback ratios fext , defined as the ratio between reinjected and emitted powers, and external cavity length Lext for which the laser becomes unstable. This presentation aims to review the recent achievements of QCLs operating under external optical feedback including the identification of the feedback regimes, the occurrence of temporal chaos with a unique scenario involving oscillations at the external cavity frequency and low-frequency fluctuations (e.g. similar to the route to chaos observed in class A gas lasers), the optical feedback originating from reflections on a chalcogenide fiber as well as the control of the mode profile in broad-area QCLs. The role of the linewidth broadening factor on the QCL?s dynamics will be also discussed [8, 9]. These results are important for the development of mid-IR optical isolators to avoid parasitic reflections, highpower lasers as well as new mid-IR applications such as chaotic LIDAR, chaos-encrypted free-space communications or unpredictable countermeasures, close to what was developed in the near-IR using chaotic laser diodes. References 1. J. Faist, Quantum cascade lasers (Oxford University Press, 2013). 2. F. P. Mezzapesa, L. L. Columbo, M. Brambilla, M. Dabbicco, S. Borri, M. S. Vitiello, H. E. Beere, D. A. Ritchie and G. Scamarcio, ?Intrinsic stability of quantum cascade lasers against optical feedback,? Opt. Express 21, 13748?13757 (2013). 3. T. Sano, ?Antimode dynamics and chaotic itinerancy in the coherence collapse of semiconductor lasers with optical feedback,? Phys. Rev. A 50, 2719?2726 (1994). 4. L. Jumpertz, M. Carras, K. Schires and F. Grillot, ?Regimes of external optical feedback in 5.6 ?m distributed feedback mid-infrared quantum cascade lasers,? Appl. Phys. Lett. 105, 131112 (2014). 5. L. Jumpertz, K. Schires, M. Carras, M. Sciamanna and F. Grillot, ?Chaotic light at mid-infrared wavelength,? Light Sci. Appl. 5, e16088 (2016). 6. D. W. Sukow, J. R. Gardner and D. J. Gauthier, ?Statistics of power-dropout events in semiconductor lasers with timedelayed optical feedback,? Phys. Rev. A 56, R3370?R3373 (1997). 7. F. Kuwashima, T. Ichikawa, I. Kitazima and H. Iwasawa, ?Chaotic oscillations in single-mode class A He-Ne laser (6328 °A) II,? Jpn. J. Appl. Phys. 38, 6321?6326 ( 1999). 8. L. Jumpertz, F. Michel, R. Pawlus, W. Elsaesser, K. Schires, M. Carras, and F. Grillot, ?Measurements of the linewidth enhancement factor of mid-infrared quantum cascade lasers by different optical feedback techniques?, AIP Advances, 6, 015212 (2016). 9. M.F. Pereira, D. O.Winge, A.Wacker, L. Jumpertz, F.Michel, R. Pawlus,W. Elsaesser, K. Schires,M. Carras, and F. Grillot, ?Nonequilibrium Green?s Functions Theory for the Alpha Factor of Quantum Cascade Lasers,? SPIE Nanosciences, (2016).