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Volume 6, Issue 2 (Suppl) J Aeronaut Aerospace Eng
ISSN: 2168-9792 JAAE, an open access journal Satellite 2017
May 11-13, 2017
May 11-13, 2017 Barcelona, Spain
3rd International Conference and Exhibition on
Satellite & Space Missions
Electron photoavalanche diode arrays: A new technology for noiseless high speed near infrared sensors
Gert Finger, Derek Ives, Leander Mehrgan and Joerg Stegmeier
European Southern Observatory, Germany
To conduct high angular resolution observations of astronomical objects from ground based observatories, adaptive optics is
needed to correct the images distorted by atmospheric turbulence. For the adaptive optics (AO) systems, low noise high speeds
near infrared sensors are needed for wave front sensing and fringe tracking. Until now the performance of those sensors was based
on CMOS detectors. Due to the high analog bandwidth needed for achieving frame rates of 1 KHz the readout noise severely limited
the sensitivity. The only way to overcome the CMOS noise barrier is the amplification of the photoelectron signal directly at the
point of absorption inside the infrared pixel by means of the noiseless avalanche gain. A breakthrough has been achieved with the
development of the near infrared SAPHIRA 320x256 pixel electron avalanche photodiode arrays (e-APD) which have already been
deployed in the wave front sensors and in the fringe tracker of the instrument Gravity at the Very Large Telescope Interferometer
(VLTI) located on Cerro Paranal in Chile. Results obtained with this new technology will be presented. The detectors now show flat
response with high quantum efficiency in the wavelength range from 0.8 μm to 2.5 um. Sub electron readout noise at frame rates of
1 KHz has been demonstrated. The dark current is as low as 0.02 e/s/pixel for an APD gain up to 8. With this performance, e-APD
arrays also have the potential to outperform conventional large format NIR science focal planes. For AO systems of extremely large
telescopes and for co-phasing segmented mirror telescopes larger formats are needed. Therefore, a 512x512 pixel SAPHIRA array
optimized for AO applications will be developed, which has 64 outputs operating at 10 Mpixel/s/output. This corresponds to frame
rates of 2 K frames/s for full single frame readout. The design of this large format SAPHIRA array will be discussed.
Figure 1: Sub-electron readout noise of Mark14 eAPD at a detector temperature of T=90K for different APD gains. Number of Fowler
pairs is proportional to detector integration time and increase by a factor of 2 for each data point. Number of Fowler pairs from left
to right: 2, 4, 8, 16, 32, 64 and 128.
Biography
Gert Finger has developed infrared arrays for astronomy and deployed them in many instruments at European Southern Observatory. He was leading the detector
group at ESO. Since his retirement, he holds an emeritus position at ESO and is still actively pushing the development of eAPD technology which has been recently
deployed in the Gravity instrument at the VLTI.
Gert Finger et al., J Aeronaut Aerospace Eng 2017, 6:2(Suppl)