Scanning of a Dissipative Kerr-Microresonator Soliton Comb for Direct Optical Frequency Comb Spectroscopy

Direct optical frequency comb spectroscopy (DFCS), which enables ultra-precise and high resolution spectroscopy, is one of the most significant applications of optical frequency combs. With the discovery of dissipative Kerr soliton combs from microresonators (Kerr soliton combs), Kerr soliton combs became compatible with chip-scale DFCS systems. However, DFCS based on Kerr soliton combs is more involved than DFCS with conventional frequency combs. This is because Kerr soliton combs typically have a mode spacing of at least tens of GHz and allow only for a small detuning range between pump laser frequency and a resonance of the microresonator. Hence the pump laser frequency needs to be carefully scanned simultaneously with the FSR of the microresonator, which is very challenging [1]. In this report, we propose a new method to overcome this difficulty with fixing the detuning, even while scanning the FSR of a microresonator. In the proposed method, a feedback loop based on Pound-Drever-Hall (PDH) locking is employed.