Modulational instability and solitons in excitonic semiconductor waveguides

Abstract

Nonlinear light propagation in a single-mode micron-size waveguide made of semiconducting excitonic material has been theoretically studied in terms of exciton polaritons by using an analysis based on macroscopic fields. When a light pulse is spectrally centered in the vicinity of the ground-state Wannier exciton resonance, it interacts with the medium nonlinearly. This optical cubic nonlinearity is caused by the repulsive exciton-exciton interactions in the semiconductor, and at resonance it is orders of magnitude larger than the Kerr nonlinearity (e.g., in silica). We demonstrate that a very strong and unconventional modulational instability takes place, which has not been previously reported. After reducing the problem to a single nonlinear Schrodinger-like equation, we also explore the formation of solitary waves both inside and outside the polaritonic gap and find evidence of spectral broadening. A realistic physical model of the excitonic waveguide structure is proposed

Spatiotemporal continuum generation in polariton waveguides

“…The polaritonic nature of our system also introduces a number of qualitative differences compared with weakly coupled systems. The strong peak in the STMI spectrum at nonzero frequency detuning Δ arises from the resonances in the phase matching introduced by the light–matter coupling, as has been theoretically predicted in the 1D (temporal only) case 46 . Furthermore, the asymptotic approach of the peak gain toward a maximum frequency at high angles is caused by the strong high-order dispersion terms 38 that arise from the anti-crossing due to the strong photon–exciton coupling.…”

“…These two patterns of radiation are well explained by the mechanisms of STMI 4,38,46 , CR 39 , and the formation of spatiotemporal X-waves 11,37,47 with different mechanisms dominating in the intermediate (Fig. 2e) and high (Fig.…”

Resonant modulational instability and self-induced transmission effects in semiconductors: Maxwell-Bloch formalism

“…The nature of these resonant peaks, which are strongly affected by the precise value of γ x , is discussed in Ref. 1. A possibility to vary J due to screening effects is shown in Sec.…”

“…The generation of coherent light at frequencies which are not easily reachable by lasers, and resonant but almost lossless soliton-like light pulse propagation in a semiconductor are remarkable and useful optical phenomena. It has been recently shown 1 that the first effect can be, in particular, realized by using the modulational instability 2 (MI) of a long light pulse (continuous wave) propagating in a semiconductor and resulting in the parametric growth of equidistant spectral sidebands. The second effect, the so-called self-induced transmission (SITm), 3 has been demonstrated both numerically and experimentally for short intense light pulses.…”

Reviving Modulational Instability with Third-Order Dispersion

“…Such models can be governed by NLSlike equation by obeying slowly-varying envelope approximation (SVEA). The phenomenon of MI has also been intensively investigated in numerous types of EP materials which include microcavities [10,11,[13][14][15]. These models generally include a term of spatial dispersion (SD) which is proportional to the Wannier-exciton mass [11].…”