Frequency and power stabilization of a three longitudinal mode He-Ne laser using secondary beat frequency

A method of frequency and power stabilization for an internal-mirror He-Ne laser using the secondary beat frequency between the three longitudinal modes is presented. Frequency and power fluctuation was ±1 MHz (2 parts in 109) and ±0.10% over 10 000 s, respectively. The square-root Allan variance between the laser stabilized in this study and the iodine stabilized He-Ne laser was 5×10−11 at average time of τ=1 s. Furthermore, we could obtain the output power of 2 mW in a single longitudinal mode.