Experimental observation of coherent cavity soliton frequency combs in silica microspheres

TL;DR

This paper reports the experimental observation of coherent cavity soliton frequency combs in silica microspheres, highlighting the importance of precise alignment and mode suppression for stable soliton formation and high coherence.

Contribution

It demonstrates the successful generation of coherent cavity soliton frequency combs in silica microspheres through careful mode management and alignment, supported by experimental and numerical evidence.

Findings

Sub-100-fs duration temporal cavity solitons

High coherence confirmed by RF noise and spectral interferometry

Solitons often form in groups with equidistant spacing

Abstract

We report on the experimental observation of coherent cavity soliton frequency combs in silica microspheres. Specifically, we demonstrate that careful alignment of the microsphere relative to the coupling fiber taper allows for the suppression of higher-order spatial modes, reducing mode interactions and enabling soliton formation. Our measurements show that the temporal cavity solitons have sub-100-fs durations, exhibit considerable Raman self-frequency shift, and generally come in groups of three or four, occasionally with equidistant spacing in the time domain. RF amplitude noise measurements and spectral interferometry confirm the high coherence of the observed soliton frequency combs, and numerical simulations show good agreement with experiments.