Effect of Raman scattering and mode coupling in Kerr comb generation in a silica whispering gallery mode microcavity

We investigated the effect of Raman scattering in multimode whispering gallery mode (WGM) microcavities. First, we discuss the competition between the effects of four-wave mixing (FWM) and stimulated Raman scattering (SRS). Thanks to the different gain bandwidths of FWM and SRS, we can switch between the FWM and SRS dominant states by changing the pump power or by changing the coupling quality factor (Q). Next, we investigated the transverse mode interaction that occurs during SRS comb formation. We found that transverse mode coupling occurred when we pumped in a low-Q mode but a comb with a single-mode family was generated when we pumped in a high-Q mode. This finding will allow us to obtain or suppress a dual comb in a single WGM microcavity. Finally, we demonstrated broad bandwidth visible light generation by third harmonic generation (THG) following the generation of a broadband SRS comb. The generation and good understanding of the SRS comb will offer us various possibilities such as dual comb generation and broad bandwidth visible light generation.