Evolution of IR detection and possible outcomes for astrophysics

Abstract

Infrared focal plane technology has evolved rapidly in the past two decades. The detector format has grown from single pixel detectors to 4K × 4K pixel arrays, and a mosaic of 4 × 4 2K × 2K pixel arrays and six mosaics of 2 × 2 2K × 2K pixel arrays are already in operation at ground based telescopes. The quantum efficiency of these arrays is close to 100%, the readout noise a few electrons rms and the dark current a few electrons per hour. However, the latent image problem has not been solved yet. A persistence model and a mitigation strategy will be discussed briefly. Specialized ASIC readout chips which digitize the multichannel video signals of large arrays directly on the focal plane are becoming available for large format arrays and they will eventually replace conventional controllers. In the mid infrared a high flux version of the MIRI detector is being developed for ground based applications. Fast low noise infrared sensors are needed for wavefront sensors of adaptive optics (AO) systems. To meet both the speed and the noise requirements two different technical approaches are being followed. One solution is the use of high gain CTIA amplifiers in the detector unit cell, the other solution is to exploit the noiseless gain mechanism of HgCdTe electron avalanche photodiode (eAPD) arrays.