First results of a cryogenic optical photon counting imaging spectrometer using a DROID array

TL;DR

This paper presents the first system test of a cryogenic optical photon counting spectrometer using a DROID array, demonstrating increased field of view and promising imaging quality despite current responsivity limitations.

Contribution

It introduces a DROID array for optical photon detection, increasing the field of view fivefold while maintaining readout channels, and evaluates its imaging performance.

Findings

Imaging quality sufficient for pattern detection

Responsivity currently too low for direct astronomical use

Knowledge gained for system optimization

Abstract

Context. In this paper we present the first system test in which we demonstrate the concept of using an array of Distributed Read Out Imaging Devices (DROIDs) for optical photon detection. Aims. After the successful S-Cam 3 detector the next step in the development of a cryogenic optical photon counting imaging spectrometer under the S-Cam project is to increase the field of view using DROIDs. With this modification the field of view of the camera has been increased by a factor of 5 in area, while keeping the number of readout channels the same. Methods. The test has been performed using the flexible S-Cam 3 system and exchanging the 10x12 Superconducting Tunnel Junction array for a 3x20 DROID array. The extra data reduction needed with DROIDs is performed offline. Results. We show that, although the responsivity (number of tunnelled quasiparticles per unit of absorbed photon energy, e- /eV) of the current array is too low for direct astronomical applications, the imaging quality is already good enough for pattern detection, and will improve further with increasing responsivity. Conclusions. The obtained knowledge can be used to optimise the system for the use of DROIDs.