Drop-port study of microresonator frequency combs: power transfer and time-domain characterization

TL;DR

This study investigates power transfer and pulse formation in silicon nitride microresonator frequency combs using a drop-port geometry, revealing smooth spectra, pump saturation effects, and passively mode-locked pulses.

Contribution

It introduces a drop-port measurement approach for microresonator combs, enabling direct observation of power transfer and pulse dynamics without filtering.

Findings

Smooth output spectra with comparable pump and comb line powers

Saturation of drop-port output power explained by pump saturation model

Observation of passively mode-locked pulses in normal dispersion microcavities

Abstract

We use a drop-port geometry to study power transfer in silicon nitride on-chip microresonator frequency comb generators. In sharp contrast with the traditional transmission geometry, we observe smooth output spectra with comparable powers in the pump and adjacent comb lines. An observation of saturation in the drop-port output power is explained semi-empirically by introducing pump saturation into a coupling of modes model. Autocorrelation measurements are performed on the drop-port output, without the need to filter out or suppress the strong pump line as is necessary in thru-port experiments. Passively mode-locked pulses are observed with a normal dispersion microcavity.