Low Noise Titanium Nitride KIDs for SuperSpec: A Millimeter-Wave On-Chip Spectrometer

TL;DR

This paper presents a new low-noise titanium nitride KID detector for SuperSpec, an on-chip millimeter-wave spectrometer, demonstrating improved sensitivity and a method to measure photon noise contributions.

Contribution

Development of a prototype TiN KID detector with enhanced sensitivity and a novel photon noise measurement method for millimeter-wave spectroscopy.

Findings

Achieved targeted R=100 resolving power.

Reported detector NEP within 10% of photon noise limit.

Demonstrated improved detector sensitivity and optical efficiency.

Abstract

SuperSpec is a novel on-chip spectrometer we are developing for multi-object, moderate resolution (R = 100 - 500), large bandwidth (~1.65:1) submillimeter and millimeter survey spectroscopy of high-redshift galaxies. The spectrometer employs a filter bank architecture, and consists of a series of half-wave resonators formed by lithographically-patterned superconducting transmission lines. The signal power admitted by each resonator is detected by a lumped element titanium nitride (TiN) kinetic inductance detector (KID) operating at 100 - 200 MHz. We have tested a new prototype device that achieves the targeted R = 100 resolving power, and has better detector sensitivity and optical efficiency than previous devices. We employ a new method for measuring photon noise using both coherent and thermal sources of radiation to cleanly separate the contributions of shot and wave noise. We report an upper limit to the detector NEP of $1.4\times10^{-17}$ W Hz$^{-1/2}$, within 10% of the photon noise limited NEP for a ground-based R=100 spectrometer.