Probing Within Partially Coherent Microcavity Frequency Combs via Optical Pulse Shaping

TL;DR

This paper investigates the coherence properties of microcavity frequency combs in a silicon nitride resonator, revealing partial coherence and the ability to probe it using optical pulse shaping.

Contribution

It introduces a method to analyze partial coherence in microcavity frequency combs by manipulating spectral phases with pulse shaping.

Findings

Partial coherence observed in microresonator combs.

Spectral phase manipulation reveals coherence variations.

Supports a model of partially coherent comb formation.

Abstract

Recent investigations of microcavity frequency combs based on cascaded four-wave mixing have revealed a link between the evolution of the optical spectrum and the observed temporal coherence. Here we study a silicon nitride microresonator for which the initial four-wave mixing sidebands are spaced by multiple free spectral ranges (FSRs) from the pump, then fill in to yield a comb with single FSR spacing, resulting in partial coherence. By using a pulse shaper to select and manipulate the phase of various subsets of spectral lines, we are able to probe the structure of the coherence within the partially coherent comb. Our data demonstrate strong variation in the degree of mutual coherence between different groups of lines and provide support for a simple model of partially coherent comb formation.