A robust, phase-sensitive system for seed laser frequency stabilization in Doppler LIDAR applications

Resonance fluorescence Doppler lidars have been instrumental to scientific understanding of the mesosphere and lower thermosphere. All 3-frequency Doppler lidars require a cw 'seed' laser with a stable and accurate carrier frequency. Since drift is inherent to tunable cw lasers, active feedback systems must be used to compensate the drift effectively. A system of PC-based laser frequency stabilization using wavelength modulation is described for Doppler lidar applications. The system has been shown to efficiently and conveniently lock a variety of seed lasers encountered in Doppler lidar to the Doppler-free spectral features of various metal vapors. This National Instruments LabVIEW-based system is described in detail, along with the spectroscopic setup. We also introduce the procedures for achieving optimal stability, methods of characterizing the performance and some common factors that may contribute to degraded performance.