Analysis of the modification of four-wave mixing phase matching by stimulated Brillouin scattering

Abstract

My thesis is a theoretical and numerical investigation of the feasibility of enhancing the four wave mixing bandwidth by tuning the phase matching condition via stimulated Brillouin scattering. This technique was experimentally demonstrated in 2013 by introducing the amplitude and phase optical gain/loss frequency responses of stimulated Brillouin scattering (SBS) pump and Stokes waves onto the FWM pump or the FWM signal. Both SBS amplitude and phase responses originate from modifying the refractive index of the optical fibre while the FWM interaction takes place. As a result the FWM phase-matching condition and hence the signal gain can be flexibly controlled. The theoretical investigation was carried out with both processes considered separately. In this thesis, we show that with modest optical power, exponential gain is achievable for normal dispersion, which leads to a gain bandwidth which is comparable in size to that for anomalous dispersion without SBS. This is equivalent to a sign change of the nonlinear contribution to the phase matching condition. However the method is limited by SBS-induced power variations and by the need to limit the SBS power levels. The thesis is illustrated while using highly nonlinear silica fibre, a well-known platform for efficient gain in telecommunications as an example. Our results can be equally applied to other materials and to other geometries, for example that of chalcogenide photonic chips, which is an interesting and exciting platform for all-optical signal processing devices. This platform is considered in Chapter 3.