Broadband anti-reflective coatings for cosmic microwave background experiments

A. Nadolski, A. M. Kofman, J. D. Vieira, P. A.R. Ade, Z. Ahmed, A. J. Anderson, J. S. Avva, R. Basu Thakur, A. N. Bender, B. A. Benson, J. E. Carlstrom, F. W. Carter, T. W. Cecil, C. L. Chang, J. F. Cliche, A. Cukierman, T. De Haan, J. Ding, M. A. Dobbs, D. DutcherW. Everett, A. Foster, J. Fu, J. Gallichio, A. Gilbert, J. C. Groh, S. T. Guns, R. Guyser, N. W. Halverson, A. H. Harke-Hosemann, N. L. Harrington, J. W. Henning, W. L. Holzapfel, N. Huang, K. D. Irwin, O. B. Jeong, M. Jonas, A. Jones, T. S. Khaire, M. Korman, D. L. Kubik, S. Kuhlmann, C. L. Kuo, A. T. Lee, A. E. Lowitz, S. S. Meyer, D. Michalik, J. Montgomery, T. Natoli, H. Nguyen, G. I. Noble, V. Novosad, S. Padin, Z. Pan, J. Pearson, C. M. Posada, W. Quan, A. Rahlin, J. E. Ruhl, J. T. Sayre, E. Shirokoff, G. Smecher, J. A. Sobrin, A. A. Stark, K. T. Story, A. Suzuki, K. L. Thompson, C. Tucker, K. Vanderlinde, G. Wang, N. Whitehorn, V. Yefremenko, K. W. Yoon, M. R. Young

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The desire for higher sensitivity has driven ground-based cosmic microwave background (CMB) experiments to employ ever larger focal planes, which in turn require larger reimaging optics. Practical limits to the maximum size of these optics motivates the development of quasi-optically-coupled (lenslet-coupled), multi-chroic detectors. These detectors can be sensitive across a broader bandwidth compared to waveguide-coupled detectors. However, the increase in bandwidth comes at a cost: the lenses (up to ∼700 mm diameter) and lenslets (∼5 mm diameter, hemispherical lenses on the focal plane) used in these systems are made from high-refractive-index materials (such as silicon or amorphous aluminum oxide) that reflect nearly a third of the incident radiation. In order to maximize the faint CMB signal that reaches the detectors, the lenses and lenslets must be coated with an anti-reflective (AR) material. The AR coating must maximize radiation transmission in scientifically interesting bands and be cryogenically stable. Such a coating was developed for the third generation camera, SPT-3G, of the South Pole Telescope (SPT) experiment, but the materials and techniques used in the development are general to AR coatings for mm-wave optics. The three-layer polytetra uoroethylene-based AR coating is broadband, inexpensive, and can be manufactured with simple tools. The coating is field tested; AR coated focal plane elements were deployed in the 2016-2017 austral summer and AR coated reimaging optics were deployed in 2017-2018.

Original languageEnglish (US)
Title of host publicationMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX
EditorsJonas Zmuidzinas, Jian-Rong Gao
PublisherSPIE
ISBN (Print)9781510619692
DOIs
StatePublished - 2018
Externally publishedYes
EventMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX 2018 - Austin, United States
Duration: Jun 12 2018Jun 15 2018

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume10708
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Other

OtherMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX 2018
CountryUnited States
CityAustin
Period6/12/186/15/18

Keywords

  • Anti-reflective coating
  • broadband
  • millimeter-wave

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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  • Cite this

    Nadolski, A., Kofman, A. M., Vieira, J. D., Ade, P. A. R., Ahmed, Z., Anderson, A. J., Avva, J. S., Basu Thakur, R., Bender, A. N., Benson, B. A., Carlstrom, J. E., Carter, F. W., Cecil, T. W., Chang, C. L., Cliche, J. F., Cukierman, A., De Haan, T., Ding, J., Dobbs, M. A., ... Young, M. R. (2018). Broadband anti-reflective coatings for cosmic microwave background experiments. In J. Zmuidzinas, & J-R. Gao (Eds.), Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX [1070843] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 10708). SPIE. https://doi.org/10.1117/12.2315674