Development of Aluminum LEKIDs for Balloon-Borne Far-IR Spectroscopy

TL;DR

This paper reports the development of aluminum-based LEKID detectors optimized for far-infrared balloon-borne spectroscopy, aiming for high sensitivity and large detector arrays to study dusty galaxies and atomic transitions.

Contribution

The paper introduces a new design and fabrication of aluminum LEKIDs with low NEP and high yield, suitable for large-format FIR spectroscopic arrays on balloons.

Findings

Achieved median NEP of 4 x 10^-18 W/Hz^0.5 in prototype detectors

Demonstrated good fabrication yield and polarization sensitivity

Designed for large arrays of ~1800 detectors for FIR spectroscopy

Abstract

We are developing lumped-element kinetic inductance detectors (LEKIDs) designed to achieve background-limited sensitivity for far-infrared (FIR) spectroscopy on a stratospheric balloon. The Spectroscopic Terahertz Airborne Receiver for Far-InfraRed Exploration (STARFIRE) will study the evolution of dusty galaxies with observations of the [CII] 158 $\mu$m and other atomic fine-structure transitions at $z=0.5-1.5$, both through direct observations of individual luminous infrared galaxies, and in blind surveys using the technique of line intensity mapping. The spectrometer will require large format ($\sim$1800 detectors) arrays of dual-polarization sensitive detectors with NEPs of $1 \times 10^{-17}$ W Hz$^{-1/2}$. The low-volume LEKIDs are fabricated with a single layer of aluminum (20 nm thick) deposited on a crystalline silicon wafer, with resonance frequencies of $100-250$ MHz. The inductor is a single meander with a linewidth of 0.4 $\mu$m, patterned in a grid to absorb optical power in both polarizations. The meander is coupled to a circular waveguide, fed by a conical feedhorn. Initial testing of a small array prototype has demonstrated good yield, and a median NEP of $4 \times 10^{-18}$ W Hz$^{-1/2}$.