Large diameter millimeter-wave low-pass filter made of alumina with laser ablated anti-reflection coating

• DOI: 10.1364/oe.444848
• Publication Date: 2021-11-19T09:00:15Z
• Authors: Ryota Takaku; Qi Wen; Scott Cray; Mark Devlin; Simon Dicker; Shaul Hanany; Takashi Hasebe; Teruhito Iida; Nobuhiko Katayama; Kuniaki Konishi; Makoto Kuwata-Gon...; Tomotake Matsumura; Norikatsu Mio; Haruyuki Sakurai; Yuki Sakurai; Ryohei Yamada; Junji Yumoto
• Keywords: Optical coating

We fabricated a 302 mm diameter low-pass filter made of alumina that has an anti-reflection coating (ARC) with laser-ablated sub-wavelength structures (SWS). The been integrated into and is operating the MUSTANG2 instrument, which coupled to Green Bank Telescope. average transmittance in band between 75 105 GHz 98%. Reflective loss due ARC 1%. difference transmission s- p-polarization states less than To within 1% accuracy we observe no variance these results when measured six independent spatial locations. replaced prior Teflon filter. Data taken heat sunk its nominal 40 K stage show performance consistent expectations: reduction about 50% filters-induced optical power load on 300 mK stage, in-band loading detectors. It 4 days laser-ablate SWS both sides disk. This first report deployed demonstration large area fabrication laser ablation.