Post on 15-Jul-2020
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?