Development of superconducting single-photon detectors at I.N.Ri.M
We are developing single-photon detectors employing superconducting-transition-edge sensors (TESs). TESs are fabricated both with Ti and proximity bilayers of Ti/ Au and the characterisitcs of the two films are compared. In the visible-near infrared spectral region, the photon absorption occurs directly in the film and the quantum efficiency of the detector is limited by the reflection losses at the film surface, which are around 60%. For many applications, like quantum cryptography, these losses are too high. In a previous paper [Nucl. Instr. Meth. A 559(2) (2006) 757 -759], we presented a way to reduce the detector reflectance for two projects based on the deposition of a few layers of amorphous silicon-nitrogen alloys. In this paper, we report some experimental data at low temperature relative to those projects. We will also show how to minimize the detector reflectance simultaneously for three telecommunication wavelengths and for a new continuum band.
single-photon tes antireflection coatings quantum communications cryogenic devices