Single Frequency Lasers for Remote Sensing

摘要

We have designed and built two versions of a space-qualifiable, single-frequency Nd:YAG laser. Our approach to frequency stabilization of the seeded oscillator is a variation of the "ramp and fire" technique. In this design, the length of the pulsed laser cavity is periodically varied until a resonance with the seed laser is optically detected. At that point the pulsed laser is fired, ensuring that it is in resonance with the seed laser. For one of the lasers the resulting single frequency pulses are amplified and frequency tripled. This system operates at 50 Hz and provides over 50 mJ/pulse of single-frequency 355 nm output. It has been integrated into the GLOW (Goddard Lidar Observatory for Winds) mobile Doppler lidar system for field testing. The second laser is a 200 Hz oscillator only system that is frequency doubled for use in the High Spectral Resolution Lidar (HSRL) system being built at NASA Langley Research Center. It provides 4 mJ of single-frequency 532 nm output that has a spectral purity of >10,000. In this paper we describe the design details, environmental testing, and integration of these lasers into their respective lidar systems.