Development of High Detection Efficiency Titanium Transition-Edge Sensors for 1550 nm Single-Photon Detection

Transition-edge sensors (TESs) have shown the capability of both energy resolution and resolving photon numbers. In this work, we present the fabrication and characterization of high detection efficiency Ti optical TESs with the critical temperature <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> = 213 mK and the photon-number resolving capability at telecommunication wavelength 1550 nm. The Ti superconducting film is prepared by a DC magnetron sputtering technique. An optical cavity comprised of 5-layers antireflection and 15-layers high-reflection Ta<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub>/SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> is enclosed with the Ti film by an ion beam assisted deposition method to improve detection efficiency, which brings the absorption of 99.74%. The energy resolution for the Ti TES with sensitive area 20 μm × 20 μm is 0.45 eV and the detection efficiency is 97% ± 1%.