Abstract. Superconducting photodetectors offer an interesting alternative to traditional photon counting systems such as photomultiplier tubes and avalanche photodiodes for applications in optical quantum information processing. In these superconducting devices, different mechanisms are exploited to detect the photon absorption, depending on the type of detector (transition edge sensor, superconducting tunnel junction and hot electron bolometer (HEB)). The first two are briefly presented; more emphasis is given on HEB elaboration made with very thin superconducting NbN films due to their unique capability of fast single-photon detection. Constraints on NbN HEB elaboration and on electronic transport properties are presented in the perspective of further improvement of the quantum efficiency in the near-infrared.

In numerous applications of optical scanning microscopy, a reference tapered fiber lens with high symmetry at sub-wavelength scale remains a challenge. Here, we demonstrate the ability to manufacture it with a wide range of geometry control, either for the length from several hundred nanometers to several hundred microns, or for the curvature radius from several tens of nanometers to several microns on the endface of a single mode fiber. On this basis, a scanning optical microscope has been developed, which allows for fast characterization of various sub-wavelength tapered fiber lenses. Focal position and depth of microlenses with different geometries have been determined to be ranged from several hundreds of nanometers to several microns. FDTD calculations are consistent with experimental results.

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