Improving Energy Detection Efficiency of Ti-Based Superconducting Transition-Edge Sensors with Optical Cavity

Superconducting transition-edge sensors (TESs) have demonstrated high detection efficiency and photon-number-resolving capability, making TESs attractive in quantum information and astrophysics. Aiming to achieve high energy detection efficiency (i.e., the ratio of the detected energy to incident energy), we integrate the TES in an optical cavity, consisting of 16-layer dielectric reflection mirror and 4-layer antireflection coating. The critical temperature was decreased to 260 mK after deposition of antireflection coating from its original 323 mK. The energy detection efficiency was increased by a factor of two, up to 40%, thanks to the enhancement of photon absorption by adding the optical cavity.