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Anti-reflection coatings for submillimeter silicon lenses

Wheeler, Jordan D. and Koopman, Brian and Gallardo, Patricio and Maloney, Philip R. and Brugger, Spencer and Cortes-Medellin, German and Datta, Rahul and Dowell, C. Darren and Glenn, Jason and Golwala, Sunil and McKenney, Chris and McMahon, Jeffrey J. and Niemack, Mike and Parshley, Steven and Stacey, Gordon (2014) Anti-reflection coatings for submillimeter silicon lenses. In: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII. Proceedings of SPIE. No.9153. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 91532Z. ISBN 978-0-8194-9621-8.

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Low-loss lenses are required for submillimeter astronomical applications, such as instrumentation for CCAT, a 25 m diameter telescope to be built at an elevation of 18,400 ft in Chile. Silicon is a leading candidate for dielectric lenses due to its low transmission loss and high index of refraction; however, the latter can lead to large reflection losses. Additionally, large diameter lenses (up to 40 cm), with substantial curvature present a challenge for fabrication of antireflection coatings. Three anti-reflection coatings are considered: a deposited dielectric coating of Parylene C, fine mesh structures cut with a dicing saw, and thin etched silicon layers (fabricated with deep reactive ion etching) for bonding to lenses. Modeling, laboratory measurements, and practicalities of fabrication for the three coatings are presented and compared. Measurements of the Parylene C anti-reflection coating were found to be consistent with previous studies and can be expected to result in a 6% transmission loss for each interface from 0.787 to 0.908 THz. The thin etched silicon layers and fine mesh structure anti-reflection coatings were designed and fabricated on test silicon wafers and found to have reflection losses less than 1% at each interface from 0.787 to 0.908 THz. The thin etched silicon layers are our preferred method because of high transmission efficiency while having an intrinsically faster fabrication time than fine structures cut with dicing saws, though much work remains to adapt the etched approach to curved surfaces and optics < 4" in diameter unlike the diced coatings.

Item Type:Book Section
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Wheeler, Jordan D.0000-0003-1678-5570
Glenn, Jason0000-0001-7527-2017
Golwala, Sunil0000-0002-1098-7174
Alternate Title:Antireflection coatings for submillimeter silicon lenses
Additional Information:© 2014 Society of Photo-Optical Instrumentation Engineers (SPIE). Date Published: 27 August 2014. This work is supported in part by the CCAT telescope project, NSF AST-118243. This work made use of the Cornell Center for Materials Research Shared Facilities, which are supported through the NSF MRSEC program (DMR-1120296). This work was performed in part at the Cornell NanoScale Facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation (Grant ECCS-0335765). We are grateful to NIST-Boulder, especially Gene Hilton and Kent Irwin, for access to their dicing-saw and imaging facilities. Charles Munson is supported by NASA grant NNX12AM32H. The development of AR coatings for silicon at Michigan is supported by NASA NNX14AB58G.
Funding AgencyGrant Number
Subject Keywords:submillimeter, artificial dielectric meta-materials, anti-reflection, Facilities: CCAT, terahertz, Parylene, SWCam, silicon, lenses
Series Name:Proceedings of SPIE
Issue or Number:9153
Record Number:CaltechAUTHORS:20150616-144926446
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Official Citation:Jordan D. Wheeler ; Brian Koopman ; Patricio Gallardo ; Philip R. Maloney ; Spencer Brugger, et al. "Antireflection coatings for submillimeter silicon lenses", Proc. SPIE 9153, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII, 91532Z (July 23, 2014); doi:10.1117/12.2057011
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58289
Deposited By: Ruth Sustaita
Deposited On:17 Jun 2015 17:02
Last Modified:09 Mar 2020 13:19

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