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 a3 He 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(τeff) of the devices at different biases and discussed the dependence of τeffon the bias. The device with a 940 μm× 940 μm continuous suspended SiN membrane demonstrated a fast response speed with τeff= 3.9 μs, which indicates a high temperature sensitivity(α = T/R· dR/dT =326). The results also showed that the TES exhibits good linearity under optical pulses of variable widths.
We successfully designed and fabricated TES bolometers utilizing Al/Ti bilayer TESs as sensitive thermometers.To reduce the intrinsic noise level and tune the saturation power of a bolometer,the TES thermometer is placed on a suspended SiN platform which is thermally coupled to the heat bath by four long SiN beams with different geometries.The measurement results show that the detectors have background limited noise performance,with a low noise equivalent power(NEP)on the order of10-17W/Hz1/2and have a saturation power of several tens pW at a bath temperature of 320 mK.These detectors are suitable for applications in ground-based astrophysics experiments by integrating absorbers for specific wavelengths.
We present the design, fabrication, and characterization of a barrier-tunable superconducting quantum interference device(SQUID) qubit for the study of Maxwell's demon experiment. In this work, a compound Josephson junction(CJJ)radio-frequency(RF)-SQUID qubit with an overdamped resistively shunted direct-current(DC)-SQUID magnetometer is used to continuously monitor the state of the qubit. The circuit is successfully fabricated with the standard Nb/Al-Al Ox/Nb trilayer process of our laboratory and characterized in a low noise measurement system, which is capable of measuring coherent dynamics of superconducting qubits, in an Oxford dilution refrigerator. All circuit parameters are determined accurately by fitting experimental data to theoretical analysis and simulation, which allows us to make a quantitative comparison between the results of the experiment and theory.
