Stimulated Raman amplification in Ga As/Al As intermixed superlattices

Abstract

We show the effectiveness of a χ(3)-quasi-phase-matched structure made of a GaAs/AlAs inter-mixed superlattice in stimulated Raman amplification for an enhancement in the output efficiency of anti-Stokes waves, where the efficiency is originally extremely small due to a phase mismatch for the anti-Stokes waves (although the output efficiency of Stokes waves is sufficiently large because of no such phase mismatch). We demonstrate that our quasi-phase matched structure enhances the anti-Stokes output efficiency up to the order of 10³ when compared with that without the quasi-phase matched structure, particularly at a small pump intensity. Here, the effects of four-wave mixing, self- and cross-phase modulations are included in addition to Raman amplification with linear optical losses. In this efficiency enhancement, we see that the output efficiency of the anti-Stokes waves is boosted via simultaneous four-wave mixing. Moreover, we show how much the effects of the self- and cross-phase-modulations degrade this efficiency enhancement. With all those effects taken into account, we show that there is an optimal superlattice length that provides the highest efficiency. In addition, we analyze the efficiency degradation due to two-photon absorption, and point out that in order to keep the highest efficiency at the optimal length, the Stokes, anti-Stokes, and pump wavelengths should be set larger than the half-bandgap wavelength of the intermixed superlattice.

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ORCID for Shinichi Saito: orcid.org/0000-0003-1539-1182

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