Raman-enabled platicon microcomb in 4H-SiC microresonator

Abstract

Stimulated Raman scattering in a Kerr microresonator is generally considered a competing nonlinear process that hinders the formation of Kerr soliton microcombs. In this work, we experimentally demonstrate that the ubiquitous Raman gain in Kerr microresonators can, in fact, be harnessed to achieve the opposite effect: it enables the formation of platicon microcomb in the normal dispersion regime, while also relaxing the conditions for soliton formation and broadening the spectrum through the simultaneous excitation of a Stokes soliton. We showcase this process in a compact silicon carbide microresonator supporting a platicon microcomb spanning 1500 to 1700 nm, with a pump-to-comb conversion efficiency as high as $56\%$. Furthermore, the presence of a Stokes soliton in the same mode family extends the comb spectrum beyond 1800 nm. By intentionally leveraging-rather than suppressing-the Raman effect, our work offers new insights into the Raman-Kerr interplay and introduces a promising approach to generating broadband platicon microcombs.