Devices and methods for measuring parameters of RFTES bolometers

Several new approaches to the measurement of intrinsic noise and dynamic characteristics of superconducting bolometers based on the RFTES technology are demonstrated. The developed methods were tested with an experimental 550–750 GHz sample at reading frequency of $\sim$1.5 GHz at a temperature of 400 mK. The absorption of thin-film resistive coatings on sapphire and quartz substrates was studied, and the emissivity of the experimental heat source was estimated as $\sim$14%. A shot noise source based on Al/AlO$_x$/Al tunnel junction was developed, and the noise temperature of the 1.35–1.6 GHz buffer amplifier referred to the detector output was determined as $\sim$ 20 K. The response time of RFTES with a hafnium film sized 6 $\times$ 2 $\times$ 0.08 $\mu$m was evaluated as $\sim$3 $\mu$s via microwave heat modulation at the second resonance at $\sim$4.2 GHz; the dynamic range at a modulation frequency of 10 kHz was more than 23 dB. The data obtained made it possible to determine the RFTES sensitivity as 1$\cdot$10$^{17}$ W/$\sqrt{Hz}$ $\pm$ 30%, that coincided with the theoretical value up to the measurement error.