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

Abstract

SuperSpec is a novel on-chip spectrometer we are developing for multiobject, 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 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 B S. Hailey-Dunsheath radiation to cleanly separate the contributions of shot and wave noise. We report an upper limit to the detector NEP of 1.4 × 10 −17 W Hz −1/2 , within 10 % of the photon noise-limited NEP for a ground-based R = 100 spectrometer.

Full-Array Noise Performance of Deployment-Grade SuperSpec mm-Wave On-Chip Spectrometers

“…We tested a 3rd-generation SuperSpec device: a 50-channel spectrometer with resolving power R ∼ 275, spanning 255-278 GHz and illustrated in Fig. 1 9,10 . Radiation incident on the device is first focused by an anti-reflection coated hyperhemispherical silicon lenslet.…”

“…In previous publications we have described the spectrometer design, filter performance, and noise characteristics for individual spectrometer channels suitable for excellent mmwave observing sites 8,9,10 . We plan to deploy a demonstration instrument to the 50-m Large Millimeter Telescope 11 (LMT) in early 2020.…”

Surface Wave Control for Large Arrays of Microwave Kinetic Inductance Detectors

“…This is a low-level effect that will become more important for large focal plane arrays or any large array requiring low pixel-pixel on chip optical crosstalk. For example, spectrometer on chip applications [29], [30], [31] also require high on chip rejection of out of band and stray radiation, so similar solutions to absorb surface wave contributions are required [32].…”

Simulating Cosmic Microwave Background Anisotropy Measurements for Microwave Kinetic Inductance Devices

“…Noise measurement for KID arrays may be done with single-tone or multi-tone methods Ref [2][3][4]. Outline of single tone read out is as follows: a single microwave tone from a synthesizer is input to a KID, where we choose the frequency to be either on resonance or off resonance.…”

“…In sub-millimeter astronomy, several groups have demonstrated the viability of MKIDs with respect to both multiplexing factors as well as noise requirements, these include SuperSpec, NIKA2 and BLAST-TNG, Refs. [2][3][4][5][6] To obtain unbiased high-precision cosmological measurements we must consider not only the absolute noise-floor of the future detectors but also their spectral shape, since cosmological parameter derivation relies on the slope and relative heights of features of Kavli Institute for Cosmological Physics, Department of Astronomy and Astrophysics at the University of Chicago, Chicago, IL, USA 60637 E-mail: ritoban@uchicago.edu the CMB spectrum. We address this issue by constructing a framework that directly connects laboratory measurements of detector noise to the cosmological parameters that we ultimately seek.…”