Broadband gain induced Raman comb formation in a silica microresonator

TL;DR

This paper investigates the formation dynamics of broadband Raman combs in silica microresonators, revealing how pump detuning and coupling influence transitions between different comb states, supported by a coupled mode model.

Contribution

It provides new insights into the formation and transition mechanisms of Raman combs in silica microresonators, which were not well understood before.

Findings

Raman combs with smooth spectral envelopes were generated.

Transitions between different Raman combs were observed and controlled.

A coupled mode model explained the observed phenomena.

Abstract

A high-Q silica whispering-gallery mode microresonator is an attractive platform on which to demonstrate a broad and phase-locked Raman comb in various wavelength regimes. Raman combs can be used for applications such as compact pulse laser sources, sensors, optical clocks, and coherence tomography. However, the formation dynamics of a Raman comb has not been well exploited. Here we study the dynamics of the Raman comb formation in silica rod microresonators, which have cavity free spectral ranges in microwave rates. We generated a Raman comb with a smooth spectral envelope and also observed the transition between two Raman combs located at different center wavelengths. The transition behavior was obtained when we changed the pump detuning and the coupling strength between the microresonator and fiber. We also explain these phenomena by using a simple model based on coupled mode equations.