Full characterization of optical Transition-Edge Sensor by impedance spectroscopy measurements in a bandwidth extending to 1 MHz

Transition-Edge Sensors (TESs) are the most promising devices as single photon detectors in the visible and infrared range. In particular ultra-fast TESs with few hundred ns response time and high quantum efficiency find application in different fields like quantum optics, quantum metrology and quantum information. The full characterization of such detectors from thermal, electrical and optical point of view is not so simple, because only some parameters are directly measurable. There are several works where various models and set of measurements are proposed to describe X- and γ-ray TES, devices with response time in the order of 100 μs. In this work, we analyze ultra-fast TES (10 μm × 10 μm area and 34 nm thick) combining for the first time TES bias curves, measurements of complex impedance, and noise measurements. In particular we perform complex impedance measurements up to 1 MHz. All the obtained results are explained using the simplest calorimeter thermal model, that is suitable for TES without external absorber.