Soliton microcombs in whispering gallery mode crystalline resonators with broadband intermode interactions

Abstract

Soliton microcombs have shown great potential in a variety of applications ranging from chip scale frequency metrology to optical communications and photonic data center, in which light coupling among cavity transverse modes, termed as intermode interactions, are long-existing and usually give rise to localized impacts on the soliton state. Of particular interest are whispering gallery mode based crystalline resonators, which with dense mode families, potentially feature interactions of all kind. While effects of narrow-band interactions such as spectral power spikes have been well recognized in crystalline resonators, effects of broadband interactions remains unexplored. Here, we demonstrate soliton microcombs with broadband intermode interactions, in home-developed magnesium fluoride microresonators with an intrinsic Q-factor approaching 10 10 . Soliton combs with featured spectral tailoring effect have been observed, which is found determined by dispersive effects of the coupled mode family. Remarkably, we demonstrate a broadband power enhanced soliton comb whose spectrum is beyond the standard soliton profile and the power efficiency is largely increased to 45%. Our results not only contribute to the understanding of dissipative soliton dynamics in multi-mode or coupled resonator systems, but also open an access to stable yet efficient soliton combs in crystalline microresonators where mode control and dispersion engineering are hardly performed.