Diode Laser Frequency Locking to an Etalon With a Double-Pass Acousto-Optic Frequency Shifter

We demonstrate an optical heterodyne spectroscopy on the reflection of an etalon using a double-pass acousto-optics frequency shifter. The experiment setup is a modified Michelson interferometer using the double-pass acousto-optics frequency shifter as the beam splitter and one etalon as the end mirror. Without using frequency modulation, the dispersion-like signal of the etalon reflection was successfully observed and optimized. Using the dispersion-like signal as an error signal, we locked a 780-nm external cavity diode laser to one resonant mode of the etalon. The estimated relative stability was ~2.6 × 10
^-10
in 0.16-s integration time.