Development of single-frequency laser for direct-detection wind lidar

摘要

Recent progress in the research of a diode pumped, single-frequency 355nm laser for direct-detection wind lidar is presented. An injection seeded Nd:YAG laser was designed and built. A 'delay-ramp-fire' technique is used to achieve single-longitudinal-mode and stable energy. In this technique, stable time relation between the resonance peak and the pump pulse is achieved by feedback controlling the delay time between the pump pulse and the ramp voltage. The resulting single frequency pulses are amplified and frequency tripled. This laser operates at 100Hz and provides 30mJ/pulse of single-frequency 355 nm output with M~2 value of ＜ 1.5. The frequency stability of the injection seeded Nd:YAG laser was investigated. The piezo hysteresis is found to be the main reason to cause the frequency unstability. In an environment avoiding high frequency vibration the frequency stability is determined by the motion linearity and ramping speed of the piezo actuator. A modified approach is proposed to improve the frequency stability of an injection seeded laser.