# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1703.10876