Self-cooling, blue-detuned dissipative Kerr microresonator soliton comb

TL;DR

This paper demonstrates a novel blue-detuned dissipative Kerr soliton microresonator that self-cools, reducing thermal noise and phase noise in microcombs, thus enhancing stability and efficiency without auxiliary lasers.

Contribution

It introduces a blue-detuned DKS generation method using avoided-mode-crossing dispersion engineering, enabling thermally robust microcombs with high efficiency and noise reduction.

Findings

Self-cooling reduces phase noise of repetition rate by up to 14.5 dB.

Achieved pump-to-comb conversion efficiency of 37%.

Demonstrated stable DKS generation on the blue-detuned side.

Abstract

Dissipative Kerr solitons (DKSs) generated in high-Q microresonators driven by continuous-wave (CW) lasers provide chip-scale optical frequency combs composed of mutually coherent CW lines. However, their small mode volume makes them highly susceptible to thermal fluctuations, and the resulting thermo-refractive noise (TRN) perturbs the repetition rate $f_{\rm rep}$. Here, we experimentally demonstrate a blue-detuned DKS in a coupled-ring microresonator. By employing avoided-mode-crossing (AMX)-induced dispersion engineering at the pump mode, DKSs are generated even when the pump laser is tuned to the higher-frequency (blue) side of the resonance. In this regime, the pump laser not only seeds DKS formation but also serves as a cooling laser for the thermally sensitive pumped mode. We observe a self-cooling effect that reduces the phase noise of $f_{\rm rep}$ by up to 14.5 dB, while achieving a pump-to-comb conversion efficiency as high as 37 %. These results establish blue-detuned DKSs as a thermally robust and power-efficient solution for integrated microcomb systems, eliminating the need for auxiliary lasers.