Automatic laser frequency stabilization to iodine absorption line

The measurement accuracy of a Doppler lidar and other laser spectra research is very sensitive to the frequency drift of the laser transmitter. Because currently used frequency locking methods usually involve complicated optics and are sensitive to the working conditions, we present a simple and robust locking method—locking the laser to iodine absorption lines with a software-based PID controller. The locking strategy was successfully applied to three kinds of cw single-frequency Nd: YAG lasers with different tuning actuators. The disadvantage of a slow tuning response is eliminated by using a parameter-adjustable PID algorithm. The frequency stability is better than 200 kHz for 3 h which, to our knowledge is one of the best long-period locking result achieved for this kind of laser.