Evaluation of a HgCdTe e-APD based detector for 2 μm CO2 DIAL application.

Abstract

Benefiting from close to ideal amplification properties (high gain, low dark current, and low excess noise factor), HgCdTe electron initiated avalanche photodiode (e-APD) technology exhibits state of the art sensitivity, thus being especially relevant for applications relying on low light level detection, such as LIDAR (Light Detection And Ranging). In addition, the tunable gap of the Hg1-xCdxTe alloy enables coverage of the short wavelength infrared (SWIR) and especially the 2μm spectral range. For these two reasons, a HgCdTe e-APD based detector is a promising candidate for future differential absorption LIDAR missions targeting greenhouse gas absorption bands in SWIR. In this study, we report on the design and evaluation of such a HgCdTe e-APD based detector. The first part focuses on detector architecture and performance. Key figures of merit are: 2.8μm cutoff wavelength, 200μm diameter almost circular sensitive area, 185K operating temperature (thermo-electric cooling), 22 APD gain (at 12V reverse bias), 360 kΩ transimpedance gain, and 60 fWHz-0.5 noise equivalent power (at 12V reverse bias). The second part presents an analysis of atmospheric LIDAR signals obtained by mounting the HgCdTe e-APD based detector on the 2μm differential absorption LIDAR developed at the Laboratoire de Météorologie Dynamique and dedicated to CO2 monitoring. Discussion emphasizes random and systematic errors in LIDAR measurements regarding breadboard detector characterization. In particular, we investigate the influence of parasitic tails in detector impulse response on short range DIAL measurements.