Measurement of microresonator frequency comb stability by spectral interferometry

TL;DR

This paper introduces a spectral interference technique to measure the spectral coherence of microresonator frequency combs, revealing different coherence regimes and supporting theoretical models with experimental data.

Contribution

A novel spectral interference method for assessing microresonator comb stability, validated through experiments and numerical simulations.

Findings

Different coherence characteristics observed in two combs

Coherence regimes align with theoretical modulation instability regimes

Experimental results agree with numerical simulations

Abstract

We demonstrate a new technique for the experimental measurement of the spectral coherence of microresonator optical frequency combs. Specifically, we use a spectral interference method, typically used in the context of supercontinuum generation, to explore the variation of the complex degree of first order coherence across the full comb bandwidth. We measure the coherence of two different frequency combs, and observe wholly different coherence characteristics. In particular, we find that the observed dynamical regimes are similar to the stable and unstable modulation instability regimes reported in previous theoretical studies. Results from numerical simulations are found to be in good agreement with experimental observations. In addition to demonstrating a new technique to assess comb stability, our results provide strong experimental support for previous theoretical analyses.