title: Millimeter-wave broadband antireflection coatings using laser ablation of subwavelength structures.
abstract: We report on the first use of laser ablation to make submillimeter, broadband, antireflection coatings (ARCs) based on subwavelength structures (SWSs) on alumina and sapphire. We used a 515 nm laser to produce pyramid-shaped structures with a pitch of about 320 μm and a total height of near 800 μm. Transmission measurements between 70 and 140 GHz are in agreement with simulations using electromagnetic propagation software. The simulations indicate that SWS-ARCs with the fabricated shape should have a fractional bandwidth response of Δν/νcenter=0.55 centered on 235 GHz for which reflections are below 3%. Extension of the bandwidth to both lower and higher frequencies, between a few tens of gigahertz and a few terahertz, should be straightforward with appropriate adjustment of laser ablation parameters.
authors.forename: Tomotake
authors.initials: T
authors.lastname: Matsumura
authors.forename: Karl
authors.initials: K
authors.lastname: Young
authors.forename: Qi
authors.initials: Q
authors.lastname: Wen
authors.forename: Shaul
authors.initials: S
authors.lastname: Hanany
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Ishino
authors.forename: Yuki
authors.initials: Y
authors.lastname: Inoue
authors.forename: Masashi
authors.initials: M
authors.lastname: Hazumi
authors.forename: Jürgen
authors.initials: J
authors.lastname: Koch
authors.forename: Oliver
authors.initials: O
authors.lastname: Suttman
authors.forename: Viktor
authors.initials: V
authors.lastname: Schütz