Comparison of Laser Receivers for Use at One Micron Wavelength

Space-based lidar instruments must be able to detect extremely weak laser return signals from orbital distance. The signals have a wide dynamic range caused by the variability in atmospheric transmission and surface reflectance under a fast moving spacecraft. Ideally, lidar detectors should be able to detect laser signal return pulses at the single photon level and produce linear output for multiple photon events. They should have high quantum efficiency in the near-infrared wavelength region where high-pulse-energy space-qualified lasers are available. Silicon avalanche photodiode (APD) detectors have been used in most space lidar receivers to date. Their sensitivity is typically hundreds of photons per pulse at 1064 nm, and is limited by the quantum efficiency, APD gain noise, dark current, and preamplifier noise. NASA is developing photon-sensitive near-infrared detectors with linear response for possible use on the next generation direct-detection space lidars. We present our measurement results and a comparison of their performance.