Frequency-scanned microresonator soliton comb with tracking of the frequency of all comb modes

Rapid and large scanning of a dissipative Kerr-microresonator soliton comb with characterization of all comb modes along with the separation of the comb modes is imperative for the emerging applications of frequency-scanned soliton combs. However, the scan speed is limited by the gain of feedback systems, and measurement of the frequency shift of all comb modes has not been demonstrated. To overcome the limitation of the feedback, we incorporate feedback with feedforward. With an additional gain of >40 dB by a feedforward signal, a dissipative Kerr-microresonator soliton comb is scanned by 70 GHz in 500 mu s, 50 GHz in 125 mu s, and 25 GHz in 50 mu s (= 500 THz/s). Furthermore, we propose and demonstrate a method to measure the frequency shift of all comb modes, in which an imbalanced Mach-Zehnder interferometer with two outputs with different wavelengths is used. Because of the two degrees of freedom of optical frequency combs, the measurement at two different wavelengths enables estimation of the frequency shift of all comb modes. (C) 2021 Optical Society of America.

Automated summary

This study introduces a feedforward signal to increase the scanning speed of a dissipative Kerr-microresonator soliton comb and proposes a method to measure the frequency shift of all comb modes using an imbalanced Mach-Zehnder interferometer with two outputs at different wavelengths.