Spectral purification of microwave signals with disciplined dissipative Kerr solitons

TL;DR

This paper demonstrates a spectral purification technique for microwave signals generated by Kerr solitons in microresonators, significantly reducing phase noise and jitter through external modulation and trapping.

Contribution

It introduces a novel method of disciplining soliton repetition rates via intracavity potential traps, leading to enhanced microwave signal purity and stability.

Findings

Long-term stability of Kerr frequency combs improved by over 4 orders of magnitude.

Phase noise reduced by 30 dB at offsets above 10 kHz.

Unexpected suppression of fast timing jitter at frequencies below cavity decay rate.

Abstract

Continuous-wave-driven Kerr nonlinear microresonators give rise to self-organization in terms of dissipative Kerr solitons, which constitute optical frequency combs that can be used to generate low-noise microwave signals. Here, by applying either amplitude or phase modulation to the driving laser we create an intracavity potential trap, to discipline the repetition rate of the solitons. We demonstrate that this effect gives rise to a novel spectral purification mechanism of the external microwave signal frequency, leading to reduced phase noise of the output signal. We experimentally observe that the microwave signal generated from disciplined solitons follows the external drive at long time scales, but exhibits an unexpected suppression of the fast timing jitter. Counter-intuitively, this filtering takes place for frequencies that are substantially lower than the cavity decay rate. As a result, while the long-time-scale stability of the Kerr frequency comb repetition rate is improved by more than 4 orders of magnitude as a result of locking to the external microwave signal, the soliton stream shows a reduction of the phase noise by 30 dB at offset frequencies above 10 kHz.