Abstract

We demonstrate microwave kinetic inductance detectors (MKIDs) whose sensitivity is limited by photon noise at signal frequencies as low as 50 mHz. The subhertz part of the detection spectrum is important for contemporary millimeter-wave science, yet photon noise below 1 Hz in MKIDs has not previously been unambiguously demonstrated. These feedhorn-coupled detectors are sensitive over a 40% fractional bandwidth centered on λ = 2 mm, are dual-polarization-sensitive, and consist of lumped-element superconducting resonators fabricated from a hybrid of stoichiometric TiN and Al films together with an amorphous-Si passivation layer. When observing a 7 K, 3.8 pW thermal load and employing no signal modulation scheme, the measured noise spectrum is white down to 50 mHz and has an amplitude consistent with photon noise. These results have implications for the development of large-format, polarization-sensitive, millimeter-wave imagers.

Highlights

  • S noise scaling, and boosting device responsitivity with engineering choices, microwave kinetic inductance detectors (MKIDs) sensitivity has rapidly improved

  • We demonstrate microwave kinetic inductance detectors (MKIDs) whose sensitivity is limited by photon noise at signal frequencies as low as 50 mHz

  • These feedhorn-coupled detectors are sensitive over a 40% fractional bandwidth centered on k 1⁄4 2 mm, are dual-polarization-sensitive, and consist of lumped-element superconducting resonators fabricated from a hybrid of stoichiometric TiN and Al films together with an amorphous-Si passivation layer

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Summary

Applied Physics Letters

E. Austermann,[1,2] M. N. Ullom,[1,2] and J. Gao[1,2]

Ultrastable detectors are particularly important for Cosmic Microwave
Findings
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