Wideband bright-soliton frequency-comb generation at optical telecommunication wavelength in a thin silicon nitride film

Abstract

Bright-soliton frequency comb generation in a thin-film silicon nitride microresonator at optical telecommunication wavelengths is numerically demonstrated using our recently developed approach for dispersion engineering by virtue of coupling dispersion between two coupled microresonators. By coupling two identical resonators through an asymmetric Mach–Zehnder structure, sinusoidal splitting of the resonance frequencies can be achieved. This enables the engineering of the dispersion of the resulting modes of the coupled structure. Using this approach, anomalous dispersion of the resonant modes can be achieved at the pumping wavelength (which is selected to be the optical telecommunication wavelength, i.e., 1.55 μm) to enable Kerr-comb generation. In addition, by utilizing soliton-induced Cherenkov radiation in the coupled-resonator structure, we can increase the bandwidth of the resulting Kerr-comb signal.