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Long Wavelength Detectors and Applications


The Long-wavelength Project develops state-of-the-art sensor arrays and multiplexed readout technology for the detection of millimeter and sub-millimeter wavelength light.  We design and fabricate superconducting integrated circuits in the Boulder Microfabrication Facility for this purpose. Applications range from fundamental physics and astrophysics to the remote detection of concealed weapons.


In recent work, we developed polarization sensitive detector arrays for a variety of applications, a main one being precision measurements of the Cosmic Microwave Background. We have focused on two sensor technologies: voltage biased transition edge sensor (TES) bolometers and Microwave Kinetic Inductance Detectors (MKIDs). A second focus area is the development of a new type of multiplexed readout, called the microwave SQUID multiplexer, which will greatly expand the sensor count of low temperature detector arrays. A third focus area is the development of a stand-off, passive THz imager for security applications. A demonstration of real-time imaging can be found in this news article.

TES polarimeter arrays
TES polarimeter arrays for Advanced ACTPol (left) and SPIDER (right).

The SOFIA airborne observatory is contained in a modified 747 jet (left). NIST's superconducting current amplifiers (right) are used in the HAWC instrument that provides SOFIA with a far-infrared imaging capability.

Major Accomplishments

  • 2017 Department of Commerce Bronze Medal Award “For the development and deployment of the world’s first multi-color cameras for measurements of the cosmic microwave background”
  • Delivery of multichroic detector arrays at 27/39 GHz, 90/150 GHz, and 150/220 GHz to Advanced ACTPol [1-4].
  • Demonstration of microwave SQUID multiplexer for application in Cosmic Microwave Background Imagers [5]. This scheme multiplexes a factor of 10 more detectors as compared to the current state-of-the-art
  • Delivery of world’s first Microwave Kinetic Inductance Detector (MKID) arrays to instrument a balloon-borne telescope [6,7]
  • Demonstration of TiN-based MKID detector at 1 mm [8]
  • Demonstration of a 'tile and trim' lithography approach to the production of MKID arrays [6]
  • Successfully designed, fabricated, and delivered TES-based arrays at 280 GHz for the balloon-borne instrument SPIDER [9]. Achieved yield is >95%, which is the highest yet of any large-format TES array [10].
  • 1st on-sky demonstration of microwave SQUID multiplexer in MUSTANG2 coupled to the Green bank telescope [11].
  • Photon noise limited sensitivity achieved in TiN-based microwave kinetic inductance detectors [12].

Recent Publications

[1] S. M. Duff et al. “Advanced ACTPol Multichroic Polarimeter Array Fabrication Process for 150 mm Wafers.” Journal of Low Temperature Physics 184 (2016):634. 

[2] S.P Ho et al. “Highly uniform 150 mm diameter multichroic polarimeter array deployed for cmb detection.”, 2017. URL

[3] S. K. Choi et al. “Characterization of the Mid-Frequency Arrays for Advanced ACT- Pol.” ArXiv e-prints (2017). 1711.04841. 

[4] B. J. Koopman et al. “Advanced ACTPol Low Frequency Array: Readout and Characterization of Prototype 27 and 39 GHz Transition Edge Sensors.” ArXiv e-prints (2017). 1711.02594. 

[5] B. Dober et al. “Microwave SQUID multiplexer demonstration for cosmic microwave background imagers.” Applied Physics Letters 111 (2017)(24):243510. 1710.04326. 

[6] C. M. McKenney et al. “Tile-and-trim micro-resonator array fabrication optimized for high multiplexing factors.” ArXiv e-prints (2018). 1803.04275. 

[7] N. Galitzki et al. “The Next Generation BLAST Experiment.” Journal of Astronomical Instrumentation 3 (2014):1440001. 1409.7084. 

[8] J. E. Austermann et al. “Millimeter-Wave Polarimeters Using Kinetic Inductance Detectors for TolTEC and Beyond.” ArXiv e-prints (2018). 1803.03280. 

[9] J. Hubmayr et al. “Design of 280 GHz feedhorn-coupled TES arrays for the balloon- borne polarimeter SPIDER.” In Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, , vol. 9914, 99140V. 2016. 1606.09396. 

[10] A. S. Bergman et al. “280 GHz Focal Plane Unit Design and Characterization for the SPIDER-2 Suborbital Polarimeter.” ArXiv e-prints (2017). 1711.04169. 

[11] S. M. Stanchfield et al. “Development of a Microwave SQUID-Multiplexed TES Array for MUSTANG-2.” Journal of Low Temperature Physics 184 (2016):460. 

[12] J. Hubmayr et al. “Photon-noise limited sensitivity in titanium nitride kinetic inductance detectors.” Applied Physics Letters 106 (2015)(7):073505. 1406.4010. 

Created March 26, 2018