Strong Negative Electrothermal Feedback in Thermal Kinetic Inductance Detectors

TL;DR

This paper demonstrates strong negative electrothermal feedback in thermal kinetic inductance detectors, enhancing response speed and linearity, with minimal non-linearity and noise below photon noise levels.

Contribution

It introduces and characterizes strong negative electrothermal feedback in TKIDs, improving their response and linearity for potential use in multiplexed detectors.

Findings

Electrothermal feedback loop gain up to approximately 16.

No detectable non-linearity over 38% incident power range.

Noise-equivalent power below the photon noise limit.

Abstract

We demonstrate strong negative electrothermal feedback accelerating and linearizing the response of a thermal kinetic inductance detector (TKID). TKIDs are a proposed highly multiplexable replacement to transition-edge sensors and measure power through the temperature-dependent resonant frequency of a superconducting microresonator bolometer. At high readout probe power and probe frequency detuned from the TKID resonant frequency, we observe electrothermal feedback loop gain up to $\mathcal L$ $\approx$ 16 through measuring the reduction of settling time. We also show that the detector response has no detectable non-linearity over a 38% range of incident power and that the noise-equivalent power is below the design photon noise.