Simple digital technique for efficient frequency locking of diode-pumped Nd:YAG lasers

A simple and easy to implement digital technique for frequency locking of a pair of diode-pumped solid state lasers is presented. The beat frequency of the two lasers, suitably prescaled, is compared to a reference oscillator. The error signal is used to drive the slave laser via its in-built PZT. An Allan variance of 1 part in 10(-6) over a typical measurement time of 0.1s, over the whole range of synthetic wavelengths of interest, proves the effectiveness of the locking system.