Near-unity absorption of near-infrared light in tungsten films

The number-resolving ability and extremely low dark-count rate of tungsten transition-edge sensors make them excellent candidates to replace avalanche photodiodes in quantum information experiments such as quantum key distribution and quantum computing at the telecommunication wavelengths, 1330 and 1550 nm. Increasing the absorption of these devices from the current value of 20% to near unity would make these detectors even more desirable for these applications. By incorporating the tungsten in a stack of elements including a mirror and an anti-reflective coating, we have demonstrated room-temperature absorption of greater than 97% in films of tungsten.