Optical EngineeringShort-pulse, coherent Doppler Nd:YAG lidar
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A short pulse (8 ns) coherent Nd:YAG lidar at 1.06 μm has been developed for 1 m range-resolved lidar measurements of high velocity (>1 km/s) aerosol or distributed targets with a Doppler shift bandwidth of up to 1 GHz. This system, which also permitted simultaneous heterodyne and direct detection, has been utilized to make, for the first time, an experimental comparison of the average carrier-to-noise ratio (CNR), signal-to-noise ratio, and standard deviation of the lidar return signals from hard targets. Nearly equal CNRs were measured with heterodyne and direct detection at a relatively short range of 450 m near the ground due to the wide electrical bandwidth (1 GHz) ofthe system. The experimental results were in good agreement with theoretical predictions that included the effects of atmospheric turbulence, and indicate the importance of atmospheric turbulence in the optimal design of a coherent lidar receiver at 1 μm.