Towards Background-Limited Kinetic Inductance Detectors for a Cryogenic Far-Infrared Space Telescope

Jason Glenn, Adalyn Fyhrie, Jordan Wheeler (CU) Peter Day, Henry “Rick” Leduc (JPL) Mike Skrutskie (Uva)

U.S. Concept for FIR Surveyor “From Early Galaxies to Habitable Planets: The Science Case and Concept for a Far-Infrared Surveyor” (L. Armus et al.) •  Post JWST, WFIRST •  5 m class, astro-

physically background limited

•  FIR spectroscopy & imaging (30 to 300 – 400 μm)

•  Photon noise-limited detector for R ≈ 1,000 NEP: 3x10-20 W/√Hz

Detector Concept Low-volume, Si lens-coupled TiN/Al bilayer, λ= 350 µμm Based on MAKO TiN devices

•  Low volume ²  Al: low resistivity è low

absorber volume for a given absorber area

²  Lens coupling è minimize area

•  τqp ~ 1 ms for Al •  Al/TiN superconducting film

²  Al Rnorm, Lkin << TiN è Rsheet & Lkin of Al

²  Resilience of TiN •  Features

²  Widths: 150 nm ²  Thicknesses: 20 nm

•  Resonances: 190 – 360 MHz

Meandered Inductor

Interdigitated Capacitor

Interdigitated Coupling Capacitor

Detector pitch: 1 mm

Fabrication at JPL Micro Devices Lab

Results

It works! •  Robust low-volume architecture demonstrated:

95% yield •  NEP = 1x10-17 W/√Hz @ 100 Hz (freq. readout) •  Photon noise limited for Popt > 1 pW, f > 10 Hz:

Work remains •  TC higher than expected (1.9 K) •  Low Qi (~2x104), short τqp (< 100 µμs)

Ø Stray light •  Excess 1/f noise below a few Hz – TLS or stray light?

Ø Not likely correlated readout-chain noise

96 pixel, 350 µμm array, detailed characterization of several LEKIDs

NEPs NEP (freq. direction) for various temperature loads

Photon Noise Limited NEPs Photon noise limited above Popt ~ 1 pW

Conclusions and Future Work

Status •  Robust low-volume, TiN/Al architecture for FIR •  NEPs1x10-17 W/√Hz, photon noise limited for P > 1 pW Future Work •  Darker testbed •  Refine  τqp measurement •  Develop better understanding of TiN/Al interaction

² Higher f0 devices to measure τqp ² Different thickness and TiN stoichiometry

•  Simulations for better understanding of optical coupling •  Consider aluminum-only devices?