Optical Solitons and Frequency Comb Generation - Abstract
Passive mode-locking (PML) is a well-known method to generate ultra-short pulses in lasers. It arises due to the incoherent absorption/gain saturation and pulse duration cannot be shorter than polarization relaxation time T2 of the gain/absorber media. In contrary, self-induced transparency mode-locking (SIT ML) or coherent mode-locking (CML) technique is based on SIT soliton (2π pulse) formation in absorber media [1-6]. It allows generating optical pulses with duration much shorter than the medium polarization relaxation time T2. SIT ML is interesting because it allows single-сycle pulse generation with ultra-high repetition rate [1, 6]. Up to now SIT ML was studied only theoretically [1-3]. In this talk, we present our recent experimental results on SIT ML in Ti:Sapphire laser with a coherent absorber cell (Rb vapors) [4-6]. We show that ML arises due to SIT pulse formation in rubidium and not due to Kerr-lens mechanism or absorption saturation. We demonstrate experimentally that pulse duration decreases with the increase of generation power due to SIT phenomenon. In standard PML lasers the situation is vice versa: pulse duration increases with the increase of generation power. Although in the experiment laser pulses have picosecond duration (which is two order of magnitude shorter than T2 in Rb), these experimental results are the first step towards realization of the PML with pulse durations, which are not limited by the absorber/amplifier line width. In addition, we study theoretically the possibility of few- and single-cycle pulse generation via SIT ML in lasers with linear cavity . Our analysis is based on numerical solution of Maxwell-Bloch equations beyond slow varying and rotative wave approximations. The generation of single-cycle pulses is relevant due to the fact that they allow the generation of unipolar pulses. Unipolar pulses can have a more efficient effect on quantum objects compared to bipolar femtosecond pulses [6-7]. A more detailed analysis of the presented results can be found in review . This work is supported by Russian Science Foundation (project 19-72-00012). 1. V.V. Kozlov, N.N. Rosanov, and S. Wabnitz, Phys. Rev. A, V.84, p. 053810 (2011). 2. R.M. Arkhipov, M.V. Arkhipov, I. Babushkin, Optics Communications, V. 361, pp. 73-78, (2016). 3. R.M. Arkhipov, M.V. Arkhipov, I. Babushkin, N.N. Rosanov, Optics Letters, V. 41(4), pp. 737-740, (2016). 4. M. V. Arkhipov, R. M. Arkhipov, A. A. Shimko, I. Babushkin, and N. N. Rosanov, JETP Lett., Vol. 109(10), pp. 634-637 (2019). 5. M.V. Arkhipov, R.M. Arkhipov, A.A. Shimko, I. Babushkin, N.N. Rosanov, submitted [arXiv preprint arXiv:1906.04587]. 6. R. M. Arkhipov, M. V. Arkhipov, A. A. Shimko, A. V. Pakhomov, N.N. Rosanov, JETP Lett. V. 110(1) (2019), in press [Pis'ma v Zh. Eksp. Teor. Fiz. V.110(1), pp. 9-20 (in Russian)]. 7. R.M. Arkhipov, A.V. Pakhomov, M.V. Arkhipov, I. Babushkin, A. Demircan, U. Morgner, N.N. Rosanov, Optics letters, V. 44 (5), pp. 1202-1205 (2019).