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 SiO
₂
/SiN
_x
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 µm× 10 µm shows an energy resolution of 0.12 eV. The TES with a large sensitive area 20 µm× 20 µm can discriminate up to 55 incident photons and the detection efficiency is 46%.