Reduction of thermal instability of soliton states in coupled Kerr-microresonators

TL;DR

This paper investigates thermal instability in silicon nitride microresonators used for frequency combs and introduces a coupled resonator system with tunable interactions to enhance soliton stability against thermal fluctuations.

Contribution

It presents experimental and simulation-based analysis of thermal effects and demonstrates a coupled microresonator approach to improve soliton stability.

Findings

Thermal response characterized via experiments and simulations.

Fast laser frequency control reduces thermal recoil.

Coupled resonator system stabilizes solitons against thermal shifts.

Abstract

Kerr-microresonator frequency combs in integrated photonics waveguides are promising technologies for next-generation positioning, navigation, and timing applications, with advantages that include platforms that are mass-producible and CMOS-compatible and spectra that are phase-coherent and octave-spanning. Fundamental thermal noise in the resonator material typically limits the timing and frequency stability of a microcomb. The small optical mode volume of the microresonators exaggerates this effect, as it both increases the magnitude and shortens the timescale of thermodynamic fluctuations. In this work, we investigate thermal instability in silicon nitride microring resonators as well as techniques for reducing their effects on the microcomb light. We characterize the time-dependent thermal response in silicon nitride microring resonators through experimental measurements and finite element method simulations. Through fast control of the pump laser frequency, we reduce thermal recoil due to heating. Finally, we demonstrate the utility of a coupled microresonator system with tunable mode interactions to stabilize a soliton pulse against thermal shifts.