Wide-Range Bolometer with RF Readout TES

TL;DR

This paper introduces a novel wide-range bolometer with RF readout based on a microbridge TES embedded in a high-Q resonator, demonstrating improved scalability and noise filtering for THz detection.

Contribution

The work presents a new thin-film detector design integrating a microbridge TES into a GHz resonator, enabling RF readout without SQUIDs and achieving high power conversion gain.

Findings

Achieved power-to-power gain above 10.

Demonstrated optical sensitivity of ~3×10⁻¹⁴ W/√Hz at 600-700 GHz.

Operated devices at about 5 K with RF characterization at 5.8 GHz.

Abstract

To improve both scalability and noise-filtering capability of a Transition-Edge Sensor (TES), a new concept of a thin-film detector is suggested, which is based on embedding a microbridge TES into a high-Q planar GHz range resonator weakly coupled to a 50 Ohm-readout transmission line. Such a TES element is designed as a hot-electron microbolometer coupled to a THz range antenna and as a load of the resonator at the same time. A weak THz signal coupled to the antenna heats the microbridge TES, thus reducing the quality factor of the resonator and leading to a power increment in the readout line. The power-to-power conversion gain, an essential figure of merit, is estimated to be above 10. To demonstrate the basic concept, we fabricated and tested a few submicron sized devices from Nb thin films for operation temperature about 5 K. The dc and rf characterization of the new device is made at a resonator frequency about 5.8 GHz. A low-noise HEMT amplifier is used in our TES experiments without the need for a SQUID readout. The optical sensitivity to blackbody radiation within the frequency band 600-700 GHz is measured as $\sim3\times 10^{-14} \textrm W/\sqrt{\textrm Hz}$ at Tc {\approx} 5 K at bath temperature ~ 1.5 K.