Observation of Gain Spiking and Nonlinear Beating of Optical Frequency Comb in a Microcavity

TL;DR

This paper investigates the transient nonlinear dynamics of Kerr microcavity optical frequency combs, revealing gain spiking and nonlinear beating phenomena that enhance understanding and stability of comb generation.

Contribution

It uncovers the internal nonlinear mechanisms, such as gain spiking and nonlinear beating, that influence comb formation and stability in Kerr microcavities for the first time.

Findings

Gain spiking caused by nonlinear phase modulation stabilizes combs.

Nonlinear beating observed through external probe demonstrates cross-phase modulation.

Transient dynamics reveal hidden nonlinear features of Kerr combs.

Abstract

Optical frequency combs are crucial for both fundamental science and applications demanding wide frequency spanning and ultra-precision resolutions. Recent advancements of nonlinear Kerr effect based optical frequency combs in microcavities open up new opportunities in a compact platform, however, internal cavity-enhanced nonlinearities are still unclear. Here we demonstrate transient nonlinear dynamics during optical frequency comb formation inside a Kerr microcavity. We show that gain spiking forms due to nonlinear phase modulation, causing comb lines' self-detuning nearby a cavity resonance, this introduces one key mechanism to stabilize optical frequency combs. Moreover, nonlinear beating has be observed by injecting an external probe to exam nonlinear cross-phase modulation between comb lines. Nonlinear transient dynamics here reveal the hidden nonlinear features of Kerr based optical frequency combs, leading to a new direction for ultrawide, ultrastable and ultrafast frequency comb generation in microcavities.