Laser stabilization to a cryogenic fiber ring resonator

The frequency stability of lasers is limited by thermal noise in state-of-the-art frequency references. Further improvement requires operation at cryogenic temperature. In this context, we investigate a fiber-based ring resonator. Our system exhibits a first-order temperature-insensitive point around 3.55 K, much lower than that of crystalline silicon. The observed low sensitivity with respect to vibrations (<5 · 10⁻¹¹ m⁻¹ s²), temperature (−22(1) · 10⁻⁹ K⁻²), and pressure changes (4.2(2) · 10⁻¹¹ mbar⁻²) makes our approach promising for future precision experiments.