Development of Feedhorn-coupled Microwave Kinetic Inductance Detectors
J. Hubmayr1, J. Beall1, D. Becker1, H.-M. Cho1, M.J. Devlin2, B. Dober2, J. Gao1, C. Groppi3, G.C. Hilton1, K.D. Irwin4, D. Li1,P. Mauskopf3, D.P. Pappas1 and M.R. Vissers1
1NIST, 2University of Pennsylvania, 3Arizona State University, and 4Stanford University
motivationFuture satellite missions operating at far infrared (FIR) wave-lengths will require high sensitivity focal plane arrays. NISThas a strong background in developing FIR detector arrays asevidenced by the delivery of the 10,000 pixel imager for theSCUBA-2 instrument on the James Clerk Maxwell Telescope.We are now developing arrays of feedhorn-coupled microwavekinetic inductance detectors (MKIDs) with the goal of achiev-ing photon-noise limited sensitivity and low-frequency stabil-ity over the range of loading conditions suitable to sub-orbitaland satellite-based observations. Current efforts are focusedon photometric applications with dual-polarization sensitivityat λ = 250 μm – 500 μm. This detector architecture will be de-ployed on the next-generation BLASTPol experiment, a NASA-funded balloon-borne polarimeter. However, we are also in-terested in exploring applications that require total intensitydetection or spectroscopy.
detection in MKIDs
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MKID are superconductors lithographically patterned into res-onant circuits. FIR photons absorbed in the superconductorchange the frequency and amplitude of the resonant circuit.These quantities are determined by homodyne measurement.Many MKIDs can be multiplexed on a single transmission line.
concept: feedhorns + MKIDsfeedhorn
arrayMKIDarray
interface
Feedhorn array (either metal or based on Si-platelets) couplesto a detector wafer containing ∼ 1000 MKIDs through a cou-pling Si wafer.
(a) (b) (c)
(d)
Feedhorn
microstrip
feedline
Si cutout for
-backshort
(SiO2 removed)
IDC inductor strips
SiO2
interface
Nb
rad
iatio
n
Cross-section schematic of sin-gle feed coupled to detector.
0KID-1
0KID-2
waveguideaperture 0KID-2
waveguideaperture
0KID-1
(a) (b)Face-on schematic of twolumped-element MKIDs, whichare sensitive to orthogonalcomponents of linear polariza-tion.
application: next-generationBLAST
Planck
BLAST SMA
BLAST’s combination of sensitivity, resolution, and mappingspeed will bridge the gap between Planck and ALMA, linkingcore magnetic fields to the Galactic field.
BLAST instrument
Detector count
λ ∆ν/ν Ndetectors Pload NEPphoton
(μm) (%) (pW) (aW/pHz)
250 30 1180 17 170350 30 490 12 120500 30 330 9 87
Balloon-borne experiment; 28-dayAntarctic flight in 2016Map magnetic fields in star forming regionsby measurement of polarized dust emission150 hours shared risk observing time
National Institute of Standards and Technology • U.S. Department of Commerce [email protected] far-IR community workshop, 2014
250 μm sub-array
10 mm
Photograph of a 5-pixel sub-array mounted in a sampleholder, which couples to a 7-pixel close-packed feed-horn array.
;a)# ;b)#
;c)#
10#mm#200#μm#
MKID design with zoom-inshowing the absorbing vol-ume within the waveguide.
Detector details
Parameter Valuematerial TiN/Ti/TiN trilayerfo 850 MHzTc 1.4 KQi 200k–400kQc ∼ 30kV 80 μm3
Acapacitor 0.9 mm3
optical band 1.0–1.4 THz
New superconducting material:TiN/Ti/TiN trilayer
(b) (c)(a)
0 2 4 6 8 10
0
1
2
3
4
5
500C TiNRT TiN
T C (K
)
N2 flow (sccm)
(a) TiN has a tuneable Tc. (b) Tc can also be tuned by varyinglayer thicknesses of TiN and Ti. (c) TiN/Ti/TiN trilayer shows betterthan 1% Tc uniformity across a 75 mm diameter wafer.
experimental configuration
THERMAL SOURCE (3K to 25K)
100mK ADR stage
LOW-‐PASS FILTER
coax in coax out
FEEDHORN ARRAY
DETECTOR WAFER
Measurement schematic of coupling the detector sub-array to a variable temperature thermal load. Thepassband is from 1.0–1.4 THz.
response to thermal load
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Power (pW)
f o (MHz
)
10−2 10−1 100 101 10210−17
10−16
Power (pW)
NEP
(W/3
Hz)
NEPmeaNEPphoton
101 103 10510−20
10−19
10−18
10−17
10−16
Frequency (Hz)
S bf/f
(Hz−
1 )
1pW 7pW 20pW
Frequency response is linear with ap-plied thermal load.
also see:"The Next GenerationBLAST Experiment"
photon-noise limitedsensitivity
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Power (pW)
f o (MH
z)
10−2 10−1 100 101 10210−17
10−16
Power (pW)
NEP
(W/3
Hz)
NEPmeaNEPphoton
101 103 10510−20
10−19
10−18
10−17
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Frequency (Hz)
S bf/f
(Hz−
1 )
1pW 7pW 20pW
Noise spectra (using frequency readout) at various thermalloads.
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Power (pW)
f o (MH
z)
10−2 10−1 100 101 10210−17
10−16
Power (pW)
NEP
(W/3
Hz)
NEPmeaNEPphoton
101 103 10510−20
10−19
10−18
10−17
10−16
Frequency (Hz)
S bf/f
(Hz−
1 )
1pW 7pW 20pW
photon-noiselimited
above 1 pW
photon-noiseprediction
National Institute of Standards and Technology • U.S. Department of Commerce [email protected] far-IR community workshop, 2014