Soliton repetition rate in a silicon-nitride microresonator

TL;DR

This paper investigates how the repetition rate of a Kerr frequency comb generated by a silicon nitride microresonator varies with pump frequency tuning, highlighting the dominant role of the Raman soliton self-frequency shift and analyzing various contributing effects.

Contribution

It provides experimental and theoretical analysis of the factors affecting soliton repetition rate, emphasizing the dominance of Raman SSFS and the independence from cavity nonlinearity and dispersion.

Findings

Raman SSFS dominates repetition rate changes

Repetition rate change is independent of cavity nonlinearity

Kerr shock has minor effect on sub-50 fs solitons

Abstract

The repetition rate of a Kerr comb comprising a single soliton in an anomalous dispersion silicon nitride microcavity is measured as a function of pump frequency tuning. The contributions from the Raman soliton self-frequency shift (SSFS) and from thermal effects are evaluated both experimentally and theoretically; the SSFS is found to dominate the changes in repetition rate. The relationship between the changes in repetition rate and pump frequency detuning is found to be independent of the nonlinearity coefficient and dispersion of the cavity. Modeling of the repetition rate change by using the generalized Lugiato-Lefever equation is discussed; the Kerr shock is found to have only a minor effect on repetition rate for cavity solitons with duration down to ~50 fs.