Development of Distributed Readout Imaging Detectors based on Superconducting Tunnel Junctions for UV/optical Astronomy
Publication date: 16 August 2000
Authors: Verhoeve, P. et al.
Journal: SPIE Proceedings - Optical and IR Telescope Instrumentation and Detectors, Masanori Iye; Alan F. Moorwood; Eds.
Volume: 4008
Page: 683-694
Year: 2000
Copyright: SPIE
Superconducting tunnel junctions (STJs) have been demonstrated as photon counting detectors in the UV-NIR wavelength range (100-1000 nm). They combine a modest wavelength resolving power with fast response and high detection efficiency over a broad wavelength band. This makes this type of detector an interesting alternative to the present generation of detectors used in UV/optical astronomy, such as CCDs and micro-channel plates. Practical applications require imaging detectors with large sensitive area and good spatial resolution. While the feasibillity of small arrays of closely packed STJs which are individually biased and read-out has already been demonstrated, the development of large format arrays is limited by the large number of electronics chains and wire connections to the cold detector which would be required. An alternative approach is to use a large area absorber combined with a few STJs at the edges or corners. A photon's energy as well as its absorption position in the absorber can be derived from the signal amplitudes measured in the STJs. In this paper the performance in terms of wavelength resolving power and position resolution of four different linear geometries of Ta absorbers, read out with Ta-Al STJs, is investigated and compared with single STJs. The UV and optical spectra obtained with the absorbers show resolving powers within a factor of two of the theoretical limit. In particular, a measured resolving power at lambda=300 nm of ~16 with a position resolution of ~9 micron is achieved with a 100x50 micron² absorber in between two 50x50 micron² STJs.
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