Simple offset frequency locking technique for pulsed CO₂ lasers

This paper first briefly overviews the current development of optical pulse offset frequency locking techniques, then summarizes the methods of discriminating frequency on optical pulse offset locking used in the techniques, and finally presents a wide-band all-digital frequency discriminating method (band width: 2-100 MHz) and design of a simple offset frequency locking system on the basis of the frequency discriminator. In addition, it also introduces the experiments on offset frequency locking between CW CO₂ laser and a pulsed CO₂ laser of which the pulse was produced by using a CdTe switch outside the optical cavity (optical pulse width: 5 μm and its repetition rate: 10 kHz). The experimental results were satisfactory, the beat frequency locking, all-digital frequency stability was 1.27×10^-7 (Allen variance).