Symmetry Breaking of Frequency Comb in Varying Normal Dispersion Fiber Ring Cavity

TL;DR

This paper demonstrates symmetry-breaking in a fiber ring cavity frequency comb by controlling birefringence, resulting in a slight increase in mode spacing and revealing complex spectral dynamics.

Contribution

First experimental demonstration of symmetry-breaking in a fiber ring cavity frequency comb with controlled birefringence and mode spacing variation.

Findings

Mode spacing increased from 0.136 nm to 0.144 nm

Spectral symmetry-breaking observed with mode spacing change

Non-uniform depletion of primary modes

Abstract

We build on a previously reported frequency comb of mode spacing 0.136 nm in a fiber ring cavity of varying normal dispersion [1], to generate, for the first time, a frequency comb of mode spacing 0.144 nm centered at 978.544 nm to demonstrate the symmetry-breaking. By controlling the birefringence of the optical cavity through fiber stretching and polarization control, the spacing of the comb lines increases from 0.136 nm to 0.144 nm, and this small change in mode spacing generates very different spectral symmetry-breaking in the frequency comb relative to the frequency comb of mode spacing 0.136 nm. Interestingly, non-uniform depletion of primary modes is also observed. The experimental results are an important contribution in the continuing effort of understanding the dynamics of frequency combs involving large number of modes, nontrivial nonlinear waves and deterministic chaos.