Sapphire, alumina, and silicon present the following characteristics that make them suitable as optical elements for millimeter and sub-millimeter applications: low-loss, high thermal conductivity at cryogenic temperatures, and high refractive index ∼3. However, the high index also leads to high reflection. We developed a technique to machine sub-wavelength structures (SWS) as a broadband anti-reflection coating on these materials through laser ablation. We describe here the status of our development: Transmission measurements of fabricated samples in a diameter of 34.5 mm agree with predictions, and we are now focusing on increasing the fabrication area with high processing rate. This is motivated by the need of ∼500 mm diameter optical elements for the next-generation cosmic microwave background polarization experiments. We show our large area machining method on the alumina and sapphire over an area of < 5200 mm2with the processing rate of < 4:0 mm3=min:, and the transmission measurements are consistent with the predictions.
|Original language||English (US)|
|Title of host publication||Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X|
|Editors||Jonas Zmuidzinas, Jian-Rong Gao|
|State||Published - 2020|
|Event||Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X 2020 - Virtual, Online, United States|
Duration: Dec 14 2020 → Dec 22 2020
|Name||Proceedings of SPIE - The International Society for Optical Engineering|
|Conference||Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X 2020|
|Period||12/14/20 → 12/22/20|
Bibliographical noteFunding Information:
We acknowledge the World Premier International Research Center Initiative (WPI), MEXT, Japan for support through Kavli IPMU. This work was supported by JSPS KAKENHI Grant Numbers JP17H01125, 19K14732, 18J20148, 18KK0083, and JSPS Core-to-Core Program, A. Advanced Research Networks. This work was also supported by the New Energy and Industrial Technology Development Organization (NEDO) project “Development of advanced laser processing with intelligence based on high-brightness and high efficiency laser technologies” by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), “Photonics and Quantum Technology for Society 5.0” and by the Center of Innovation Program, from Japan Science and Technology Agency, JST.
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- broadband anti-reection
- laser ablation