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 L≈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.
Highlights
AND MOTIVATIONWe present observations of strong negative electrothermal feedback in a thermal kinetic inductance detector (TKID)
The resonant frequency is measured through the phase shift of a readout probe signal, which normally is at a low enough power such that the TKID dynamics are not altered by the probe
We studied a single TKID at high readout probe powers using the cryostat described in Wandui et al[15] and the softwaredefined radio system described in Minutolo et al[23]
Summary
We present observations of strong negative electrothermal feedback in a thermal kinetic inductance detector (TKID). Detuning the probe frequency above the TKID’s resonant frequency, an increase in temperature of the suspended absorber decreases the resonant frequency due to an increase in kinetic inductance, moving the resonant frequency further from the probe frequency This decreases the electrical power dissipated by the probe in the resonator, which in turn decreases the temperature of the suspended absorber, resulting in negative electrothermal feedback. The feedback can be strong in resonators with high quality factors, as there is a large change in absorption of power from the probe signal for a small change in resonant frequency
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