Mechanical control of a microrod-resonator optical frequency comb

TL;DR

This paper demonstrates the stabilization of a microresonator-based optical frequency comb using mechanical actuation, achieving record stability and precise control over comb line spacing, advancing microcomb technology for integrated systems.

Contribution

It introduces a novel mechanical stabilization method for microcombs, achieving unprecedented stability and control over comb line spacing in microresonator systems.

Findings

Record residual fluctuation of $5\times10^{-15}$ for 1 s averaging.

Effective stabilization of spectral slices with <0.5 mHz variation.

Successful fabrication of microrod resonators using CO$_2$-laser-machining.

Abstract

Robust control and stabilization of optical frequency combs enables an extraordinary range of scientific and technological applications, including frequency metrology at extreme levels of precision, novel spectroscopy of quantum gases and of molecules from visible wavelengths to the far infrared, searches for exoplanets, and photonic waveform synthesis. Here we report on the stabilization of a microresonator-based optical comb (microcomb) by way of mechanical actuation. This represents an important step in the development of microcomb technology, which offers a pathway toward fully-integrated comb systems. Residual fluctuations of our 32.6 GHz microcomb line spacing reach a record stability level of $5\times10^{-15}$ for 1 s averaging, thereby highlighting the potential of microcombs to support modern optical frequency standards. Furthermore, measurements of the line spacing with respect to an independent frequency reference reveal the effective stabilization of different spectral slices of the comb with a $<$0.5 mHz variation among 140 comb lines spanning 4.5 THz. These experiments were performed with newly-developed microrod resonators, which were fabricated using a CO$_2$-laser-machining technique.