Ultrahigh-frequency stabilization of a diode-pumped Nd:YAG laser with a high-power-acceptance photodetector

We describe the ultrahigh-frequency stabilization of a diode-pumped Nd:YAG laser by use of a high-power-acceptance photodetector. The photodetector, which is constructed with an optical power divider and eight combined photodiodes, is developed to reduce shot-noise-limited FM noise. The laser frequency is locked to a Fabry–Perot cavity with a finesse of 25,600 by the Drever–Hall technique. By using the optical power of 47 mW at the photodetector, we reduce the relative FM noise at the error signal to the shot-noise limit of $4.2\times {10}^{-5}\hspace{0.17em}\text{Hz}/\sqrt{\text{Hz}}$ below the Fourier frequency of 500 Hz.