Untitled - Laboratoire d'Astrophysique de l'Observatoire de Grenoble

Figure 11.10: thermal modeling of WIRCam using FEA analysis and the Ideas/TMG thermal modelling
software. Left: thermal model in the steady state of the filter wheels cage and the optical barrel; right:
thermal model of the cold finger which transmits the cryogenic power to the cold structure.
• Devices simpler to manufacture, low cost (one single active layer)
• Far higher speed (1 GHz instead of 10 kHz)
• Developments supported by numerous practical applications, including commercial ones, contrary to STJ.
Superconducting Single Photon Detectors (SSPD) Niobium Nitride (NbN) Superconducting Single-
Photon Devices are sensitive to radiation from UV to mid-IR. In terms of speed and sensitivity, they outperform
any semiconductor and superconducting photon counters. They reach Quantum Efficiency (QE) of 20-30% at
wavelengths of [1.3 µm; 1.55 µm], related to intrinsic QE close to 100%. Dark counting rate is extremely
low: 10 −4 counts per second and less. Measured Noise Equivalent Power (NEP) is about 5.10 −21 W/ √ Hz in
a wavelength range of [0.5 µm; 1.5 µm]. NbN SSPD is practical devices for non-invasive optical analysis of
CMOS circuits and can be successfully used for quantum communications and quantum cryptography. These
new detectors are developed in a collaboration with the CEA Grenoble and the Laboratoire de Spectrométrie
Physique de Grenoble. Some first devices have been recently produced (Figure 11.11) and are currently under
performance evaluation. These detectors are particularly interesting for the Lippmann spectral detectors (see
Prospective).
Figure 11.11: Left: 3x3 pixel array of 30 µm x 30 µm Ta-based STJ’s. Upper middle: details of the
array structure with a Scanning Electron Microscope (SEM). Lower middle: single Ta-STJ. Right Scanning
Electron Microscope (SEM) photography of a SSPD meander fabricated at the CEA-Grenoble. The width of
the stripes and the distance between them are 150 nm. Courtesy of CEA-Grenoble/DRFMC/LCP (Jean-Claude
Villégier).
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