Photon-noise limited sensitivity in titanium nitride kinetic inductance detectors
Abstract
We demonstrate photon-noise limited performance at sub-millimeter wavelengths in feedhorn-coupled, microwave kinetic inductance detectors (MKIDs) made of a TiN/Ti/TiN trilayer superconducting film, tuned to have a transition temperature of 1.4~K. Micro-machining of the silicon-on-insulator wafer backside creates a quarter-wavelength backshort optimized for efficient coupling at 250~. Using frequency read out and when viewing a variable temperature blackbody source, we measure device noise consistent with photon noise when the incident optical power is >~0.5~pW, corresponding to noise equivalent powers >~3× 10-17 W/Hz. This sensitivity makes these devices suitable for broadband photometric applications at these wavelengths.
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