Broadband Fabry–Pérot Resonator From Zerodur for Laser Stabilisation Below 1KHZ Linewidth With < 100 HZ/S Drift and Reduced Sensitivity to Vibrations

Here we demonstrate the results of creating a two-mirror Fabry-Pérot resonator (FPR) that allows achieving the spectral width of a stabilised laser line below 1 kHz. It had low expansion Zerodur spacer and broadband high reflectance mirrors (99.85% in the range of 630 to 1140 nm). FPR was vertically mid-plane mounted for reduced sensitivity to vibrations and included in two shields inside a vacuum chamber to lower temperature fluctuations. Peltier element was used for temperature stabilisation at zero-expansion temperature. Pound-Drever-Hall (PDH) technique was applied. The signal from FPR was compared to ultra-stable signal (of about 1 Hz linewidth) to form a beat note signal. For the best performance, width of the beat note signal was below 1 kHz with the linear drift of about 23 Hz/s at 780 nm. The Allan deviation showed relative stability of the signal to be about 1 × 10^-12.