Optical response of Al/Ti bilayer transition edge sensors

We report the optical response characteristics of Al/Ti bilayer transition edge sensors (TESs), which are mainly comprised of Al/Ti bilayer thermometers and suspended SiN membranes for thermal isolation. The measurement was performed in a ³He sorption refrigerator and the device's response to optical pulses was investigated using a pulsed laser source. Based on these measurements, we obtained the effective recovery time (τ _eff) of the devices at different biases and discussed the dependence of τ_eff on the bias. The device with a 940 μm × 940 μm continuous suspended SiN membrane demonstrated a fast response speed with τ _eff = 3.9 μs, which indicates a high temperature sensitivity (α = T/R ·d R/dT = 326). The results also showed that the TES exhibits good linearity under optical pulses of variable widths.