Novel Detection Scheme for Cryogenic Bolometers With High Sensitivity and Scalability

Cryogenic bolometers based on thin silicon nitride detector applications, particularly in the field of submillimeter-wave imaging. For that, transition-edge sensors (TESs) have been established as a viable approach toward developing multipixel sensor arrays. However, current multiplexer techniques as time- or code-division multiplexing do not scale well to multiplexing levels of several hundred detectors per channel. To achieve such a scalable readout solution, frequency-division multiplexing (FDM) would be an applicable way. For that, the temperature-sensing element of a bolometer has to be resonant or coupled to a resonance circuit, which changes its microwave behavior with the temperature of the absorber. The design of a useful resonant readout circuit (RRC) follows the same rules as for lumped-element kinetic inductance detectors (KIDs). High-quality factors and low crosstalk are required to achieve a high spectral packing density and a clear determination of the individual detuning of RRC. This is necessary to be able to read out large arrays within a limited readout bandwidth. We call this novel combination of an RRC as the temperature-sensing element and a cryogenic bolometer as a kinetic inductance bolometer. It combines the high sensitivity of a TES with the FDM readout capability of a KID together in one device. In this paper, we demonstrate the proof of principle of such novel devices. The devices were fabricated with niobium thin-film technology on silicon substrates and measured in a cryostat at 4.2 K.We present first measurement results, including noise equivalent power (NEP).