Development of Ti/Au Transition-Edge Sensors for Single-Photon Detection

Transition-edge sensors (TESs) have shown remarkable energy resolution and photon-number resolving ability. In this paper, we report the fabrication and characterization of Ti/Au optical TESs for the detection of single photon at the telecommunication wavelength 1550 nm. A SiO2/SiNx antireflection coating is deposited on top of TESs by an inductively coupled plasma-assisted plasma-enhanced chemical vapor deposition (ICP-PECVD) process to improve the detection efficiency. Ti/Au (50/60 nm) TES with a small sensitive area 10 mu mx 10 mu m shows an energy resolution of 0.12 eV. The TES with a large sensitive area 20 mu mx 20 mu m can discriminate up to 55 incident photons and the detection efficiency is 46%.