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 ($<5\cdot{ 10^{ -11}}\,\text{ m}^{ -1} \text{ s}^{ 2}$), temperature ($-22(1)\cdot{ 10^{ -9}}\,\text{ K}^{ -2}$) and pressure changes ($4.2(2)\cdot{ 10^{ -11}}\,\text{ mbar}^{ -2}$) makes our approach promising for future precision experiments.
Categories: physics.optics physics.atom-ph physics.ins-det quant-ph