Frequency control and monitoring of the ALOMAR RMR lidar's pulsed high-power Nd:YAG lasers

Abstract. Doppler wind measurements in the middle atmosphere by ground-based lidar are challenging and benefit from precise spectral characterization of the laser source. We present a system for frequency control and monitoring of pulsed commercial high-power Nd:YAG lasers, which is entirely software controlled, automated, and works in real-time. It basically consists of an embedded controller handling the cavity control of the injection-seeded power laser and an embedded controller based spectrometer performing the spectral analysis of each individual power laser pulse using a Fabry-Pérot etalon. The power laser cavity length is optimized by pulse build-up time minimization, yielding a stable long-term single-mode operation. The spectrometer is able to analyze continuous-wave as well as pulsed lasers with repetition rates of 100 Hz and resolves frequency changes of less than 300 kHz, corresponding to a resolution of ∼ 5 × 10−10 at a wavelength of 532 nm.