Interference Filters and Coatings for Mid-Infrared Astronomy (8-30μm)

  • Gary J. Hawkins, Roger Hunneman, Richard Sherwood, Barbara M. Barrett
  • February 2003, SPIE
  • DOI: 10.1117/12.458056

Mid-Infrared Filters for Astronomy

What is it about?

Infrared bandpass filters have been developed in the N-(λ=7.5-14μm) and Q-(λ=16-28μm) band mid-IR atmospheric windows to study interstellar and circumstellar environments crucial for star and planetary formation theories.

Why is it important?

The VISIR instrument for the European Southern Observatory (ESO) Very Large Telescope (VLT) is a thermal-infrared imager and spectrometer currently being developed by the French Service d'Astrophysique of CEA Saclay, and Dutch NFRA ASTRON Dwingeloo consortium.


Dr Gary J Hawkins
University of Reading

This paper describes the design and fabrication methods used to manufacture these astronomical consortium filters, including the rationale for the selection of multilayer coating designs, temperature-dependant optical properties of the filter materials and FTIR spectral measurements showing the changes in passband and blocking performance on cooling to <50K. We also describe the development of a 7-14μm broadband antireflection coating deposited on Ge lenses and KRS-5 grisms for cryogenic operation at 40K.

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The following have contributed to this page: Dr Gary J Hawkins and Mr Richard E Sherwood