Photon-noise limited sensitivity in titanium nitride kinetic inductance detectors

TL;DR

This paper demonstrates that titanium nitride kinetic inductance detectors can achieve photon-noise limited sensitivity at sub-millimeter wavelengths, making them suitable for broadband photometry.

Contribution

It introduces a TiN/Ti/TiN trilayer superconducting film MKID with optimized backshort for efficient coupling and photon-noise limited performance at 250 microns.

Findings

Photon-noise limited performance achieved at incident powers > 0.5 pW

Noise equivalent power > 3×10^{-17} W/√Hz

Suitable for broadband sub-millimeter photometric applications

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~\micron. 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$\times 10^{-17}$ W/$\sqrt{\mathrm{Hz}}$. This sensitivity makes these devices suitable for broadband photometric applications at these wavelengths.