We have developed epoxy-based, broadband antireflection coatings for millimeter-wave astrophysics experiments with cryogenic optics. By using multiple-layer coatings where each layer steps in dielectric constant, we achieved low reflection over a wide bandwidth. We suppressed the reflection from an alumina disk to 10% over fractional bandwidths of 92% and 104% using two-layer and three-layer coatings, respectively. The dielectric constants of epoxies were tuned between 2.06 and 7.44 by mixing three types of epoxy and doping with strontium titanate powder required for the high dielectric mixtures. At 140 K, the band-integrated absorption loss in the coatings was suppressed to less than 1% for the two-layer coating, and below 10% for the three-layer coating.
© 2013 Optical Society of America
Original Manuscript: July 31, 2013
Revised Manuscript: October 20, 2013
Manuscript Accepted: October 23, 2013
Published: November 18, 2013
Darin Rosen, Aritoki Suzuki, Brian Keating, William Krantz, Adrian T. Lee, Erin Quealy, Paul L. Richards, Praween Siritanasak, and William Walker, "Epoxy-based broadband antireflection coating for millimeter-wave optics," Appl. Opt. 52, 8102-8105 (2013)