  There have been no significant breakthroughs in infrared imagery since the
hybridization of III-V or II-VI narrow-bandgap semiconductors on complementary
metal-oxide semiconductor (CMOS) read-out integrated circuits (ROICs). The
development of third-generation, linear-mode avalanche photodiode arrays
(LmAPDs) using mercury cadmium telluride (MCT) has resulted in a significant
sensitivity improvement for short-wave infrared (SWIR) imaging. The first
dedicated LmAPD device, called SAPHIRA (320x256/24 microns), was designed by
Leonardo UK Ltd specifically for SWIR astronomical applications. In the past
decade there has been a significant development effort to make larger LmAPD
arrays for low-background astronomy. Larger LmAPD formats for ultra-low
noise/flux SWIR imaging, currently under development at Leonardo include a 512
x 512 LmAPD array funded by ESO, MPE and NRC Herzberg, a 1k x 1k array funded
by NASA and a 2K x 2K device funded by ESA for general scientific imaging
applications. The 2048x2048 pixel ROIC has a pitch of 15 microns, 4/8/16
outputs and a maximum frame rate of 10 Hz. The ROIC characterization is
scheduled in the third quarter of 2022, while the first arrays will be
fabricated by end-2022. The hybridized arrays will be characterized during
end-2022. At this time, First Light Imaging will start the development of an
autonomous camera integrating this 2Kx2K LmAPD array, based on the unique
experience from the C-RED One camera, the only commercial camera integrating
the SAPHIRA SWIR LmAPD array.The detector will be embedded in a compact high
vacuum cryostat cooled with low vibration pulse at 50-80K which does not
require external pumping. Sub-electron readout noise is expected to be achieved
with high multiplication gain. Custom cold filters and beam aperture cold
baffling will be integrated in the camera.
