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Free keywords:
Astronomy & Astrophysics; Instruments & Instrumentation; Optics; nondestructive readout; Fowler sampling; readout noise; signal-to-noise
ratio; avalanche photodiode; e(-)APD; LmAPD; HgCdTe; near-infrared;
wavefront sensor; fringe tracker; GRAVITY; Hawaii-2RG; JWST;
Abstract:
For infrared detectors a new nondestructive multiple sampling technique of the detector integration ramp has been developed. It improves the duty cycle of observations by a factor of two if the integration ramp is sampled with the maximum possible number of nondestructive readouts, and several exposures are averaged to improve the sensitivity. The sampling method has been tested with the bare ROIC of the large SAPHIRA detector at room temperature, but this mode can also be applied to Hawaii-2RG, Hawaii-4RG and other infrared detectors. If the frame rate permits multiple nondestructive readouts, it is also well suited for near-infrared eAPD arrays used for NIR adaptive optics and fringe tracking. A paradigm change of detector testing is proposed: Instead of optimizing single parameters, such as the read noise, the signal-to-noise ratio of a faint image pattern should be optimized, as presented here by an experiment. For a given exposure time the signal-to-noise ratios of the new readout mode and conventional Fowler sampling are compared.
