A silicon single-crystal cryogenic optical resonator

TL;DR

This paper demonstrates a silicon cryogenic optical resonator operating at 1.5 K, achieving high stability and enabling ultra-precise laser frequency stabilization with potential for low-$10^{-17}$ level accuracy.

Contribution

It introduces a robust silicon cryogenic resonator with unprecedented stability and detailed thermal expansion measurements at millikelvin temperatures.

Findings

Absolute frequency drift less than 20 Hz over 1 hour

Thermal expansion coefficient $eta$ measured at 1.6 K and 16.8 K

Potential for laser frequency stabilization at the low-$10^{-17}$ level

Abstract

We report on the demonstration and characterization of a silicon optical resonator for laser frequency stabilization, operating in the deep cryogenic regime at temperatures as low as 1.5 K. Robust operation was achieved, with absolute frequency drift less than 20 Hz over 1 hour. This stability allowed sensitive measurements of the resonator thermal expansion coefficient ($\alpha$). We found $\alpha=4.6\times10^{-13}$ ${\rm K^{-1}}$ at 1.6 K. At 16.8 K $\alpha$ vanishes, with a derivative equal to $-6\times10^{-10}$ ${\rm K}^{-2}$. The temperature of the resonator was stabilized to a level below 10 $\mu$K for averaging times longer than 20 s. The sensitivity of the resonator frequency to a variation of the laser power was also studied. The corresponding sensitivities and the expected Brownian noise indicate that this system should enable frequency stabilization of lasers at the low-$10^{-17}$ level.