Compression of femtosecond pulses into dissipative few-cycle optical solitons in coherent nonlinear resonant media

Abstract

A composite resonant material consisting of amplifying and absorbing two-level quantum dots in a semiconductor host with conductive loss compresses a femtosecond pulse down to one-two optical cycles forming stable solitons. IntroductionThe rapidly expanding range of applications stemming from the recent progress in attosecond physics 1 and extreme nonlinear optics 2 requires both high-power as well as ultra-broadband sources of electromagnetic pulses. Obtaining such pulses calls for the development of a new class of laser sources, in side-step with the elaboration of advanced theoretical methods, with the scope of extending the boundaries of present-day light sources towards higher energies and shorter durations. In this work we propose and analyze a type of source which is capable of generating powerful few-cycle pulses. For its adequate description, we develop a theoretical model which abandons virtually all of the approximations that are typically used in nonlinear optics.The dissipative solitons reported here have historical predecessors in the form of both ultrabroadband video-pulses and few-cycle dissipative solitons, 3 which were separately found for different implementations of the resonant level structure of the active and passive centers, and for different loss mechanisms. Such type of pulses are reviewed and properly referenced in Ref. 4 .By powerful pulses we mean pulses that are able to induce power broadening comparable in width to the value of the optical frequency itself (≈ 1 eV), but not yet powerful enough to ionize the atom (< 10 eV), so that the atomic structure of levels is adequately described by the unperturbed atomic Hamiltonian. The durations τ p of these pulses reach the value of the inverse optical frequency ω 0 : τ p ≈ ω −1 0 , thus invalidating the usual rotating wave and slowly-varying approximations. In this analysis we consider pulses that are incident from vacuum on the boundary with a moderately dense medium, whose resonantlyenhanced index of refraction is sizable enough to cause an appreciable reflection from the bound-