MCT APD focal plane arrays for astronomy at CEA-LETI

HgCdTe avalanche photodiodes offers a new horizon for observing spatial or temporal signals of a low number infrared photons, enabling new IR science, telecommunication and defence applications. A large number of HgCdTe APD based detectors have been developed at CEA LETI to address the increasing number of applications in which a faint photonic information needs to be extracted from the noise of the proximity electronics used to sample the signal. In most astronomical applications, the low photon flux requires long observation times to acquire a photon shot noise limited signal. The use of MCT APDs enables a reduction of the required observation time but the noise of the diode dark current still needs to be very low in most applications. A number of these detectors have been developed for or can be used in astronomical applications and we present the dark current and gain dependent sensitivities obtained with four different HgCdTe APDs focal plane arrays (FPAs) of different formats, capable of addressing astronomical applications such as wavefront sensing, interferometry, spectroscopy and imagery.