To realize optical quantum computer, it is required to develop a photon-number-resolving detector with small time jitter in the near infrared or communication wavelength. Transition Edge sensors (TESs) are promising photon-number-resolving detectors for near infrared photons, which can realize high energy resolution, a low time energy threshold, a high quantum efficiency, and a low dark count rate.　TESs can show better energy resolution by lowering the transition temperature and reducing the heat capacity. In this study, we plan to improve the performance of the TES by reducing the heat capacity of the TES and evaluate the energy resolution and the photon number resolution, We formed a silicon wafer into a racket-like shape which matches the inner diameter of optical fiber sleeve in order to improve the alignment between optical fiber and the sensitive area of TES.

Fig. 1 shows a setup of the detector with a magnified image of the fabricated TES.

We have fabricated 1μm x 1μm, 2μm x 2μm , 3μm x 3μm TESs. We will show the characteristics and energy resolution of these TESs

Keywords: Transition Edge Sensors, infrared single photon, photon number resolving, microfabrication