Parallel Plate Capacitor Aluminum KIDs for Future Far-Infrared Space-Based Observatories

TL;DR

This paper reports on the development and laboratory characterization of aluminum KID arrays optimized for future far-infrared space observatories, demonstrating photon noise limited performance at extremely low optical powers.

Contribution

It introduces a novel low-volume aluminum KID design with a compact parallel plate capacitor and a resonant absorber, achieving near photon noise limited sensitivity in the far-infrared band.

Findings

Photon noise limited down to 50 aW

Limiting NEP of 6.5 x 10^-19 W/Hz^1/2

Optical system well characterized at low background

Abstract

Future space-based far-infrared astrophysical observatories will require exquis-itely sensitive detectors consistent with the low optical backgrounds. The PRobe far-Infrared Mission for Astrophysics (PRIMA) will deploy arrays of thousands of superconducting kinetic inductance detectors (KIDs) sensitive to radiation between 25 and 265 $\mu$m. Here, we present laboratory characterization of prototype, 25 -- 80 $\mu$m wavelength, low-volume, aluminum KIDs designed for the low-background environment expected with PRIMA. A compact parallel plate capacitor is used to minimize the detector footprint and suppress TLS noise. A novel resonant absorber is designed to enhance response in the band of interest. We present noise and optical efficiency measurements of these detectors taken with a low-background cryostat and a cryogenic blackbody. A microlens-hybridized KID array is found to be photon noise limited down to about 50 aW with a limiting detector NEP of about $6.5 \times 10^{-19}~\textrm{W/Hz}^{1/2}$. A fit to an NEP model shows that our optical system is well characterized and understood down to 50 aW. We discuss future plans for low-volume aluminum KID array development as well as the testbeds used for these measurements.