Tungsten transition-edge sensors for IR/optical/UV photon counting

Tungsten transition-edge sensors have been demonstrated to have impressive photon-counting capabilities. Of particular interest is the expected impact to the applications of low-flux astronomy and photonic quantum information. The combination of high quantum efficiency, negligible dark count rate, and moderate energy resolution is unique among IR/optical/UV single-photon detectors and has enabled a new class of measurements to be performed for the first time. This paper gives a background on tungsten TES (W-TES) technology and major applications and discusses recent progress at NIST toward devices with improved optical efficiency. (author)