Laser frequency instability of 2 × 10⁻¹⁶ by stabilizing to 30-cm-long Fabry-Pérot cavities at 578 nm

Laser light at 578 nm is frequency-stabilized to two independent 30-cm-long Fabry-Pérot cavities. To achieve a thermal-noise-limited cavity length stability, the geometry and support configuration of the Fabry-Pérot cavities are optimized. The fractional frequency instability of each cavity-stabilized laser system is 2 × 10⁻¹⁶ at 1 s averaging time, approaching to the thermal-noise-induced length instability of the reference cavity. The most probable linewidth of each laser system is about 0.2 Hz, and the laser frequency noise at Fourier frequency of 1 Hz is 0.1 Hz/Hz.