Coherence properties of Kerr frequency combs under noisy injection and optical feedback

Abstract

Kerr frequency combs in high-Q optical microresonators hold great promise for precision metrology, high-speed communications, and low-noise photonics. Understanding their coherence properties is essential for realizing compact, energy-efficient, and low-noise light sources. The in- terplay between pulsed injection, intrinsic and external noise, and optical feedback plays a central role in achieving highly coherent microcombs. Here, we study the coherence dynamics of Kerr frequency combs under continuous-wave (CW) and pulsed pumping within the framework of the Lugiato?Lefever equation. Using asymptotic analysis, we quantify the phase noise and timing jit- ter induced by pump source fluctuations and thermal noise. Numerical simulations further reveal comb degradation due to CW pump noise, while the inclusion of optical feedback restores the comb and narrows the linewidth through a mechanism analogous to that of external-cavity lasers