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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0

P

f0

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fr

frf

(c)

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(f)(a)

(b) S21

Lki

h1 2(g)(d)

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h1 2(g)(d)

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 hubmayr@nist.gov 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

0 10 20848.4

848.5

848.6

848.7

848.8

848.9

849

849.1

849.2

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

0 10 20848.4

848.5

848.6

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848.8

848.9

849

849.1

849.2

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

Noise spectra (using frequency readout) at various thermalloads.

0 10 20848.4

848.5

848.6

848.7

848.8

848.9

849

849.1

849.2

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 hubmayr@nist.gov far-IR community workshop, 2014