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Proceedings Paper

Fabrication of 721-pixel silicon lens array of an MKID camera
Author(s): Kenji Mitsui; Tom Nitta; Norio Okada; Yutaro Sekímoto; Kenichi Karatsu; Shigeyuki Sekiguchi; Masakazu Sekine; Takashi Noguchi
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Paper Abstract

We have been developing a lens-integrated superconducting camera for millimeter and submillimeter astronomy. High-purity silicon (Si) is suitable for the lens array of the Microwave Kinetic Inductance Detector (MKID) camera due to the high refractive index and the low dielectric loss at low temperature. The camera is antenna-coupled Al coplanar waveguides on a Si substrate. Thus the lens and the device are made of the same material. We report a fabrication method of 721 pixel Si lens array with anti-reflection coating. The Si lens array was fabricated with an ultra-precision cutting machine. It uses TiAlN coated carbide end mills attached with a high-speed spindle. The shape accuracy was less than 50 μm peak-to-valley and the surface roughness was Ra 1.8 μm. The mixed epoxy was used as anti-reflection coating to adjust the refractive index. It was shaved to make the thickness of 185 μm for 220 GHz. Narrow grooves were made between the lenses to prevent cracking due to different thermal expansion coefficients of Si and the epoxy. The surface roughness of the anti-reflection coating was Ra 2.4 ~ 4.2 μm.

Paper Details

Date Published: 23 July 2014
PDF: 10 pages
Proc. SPIE 9153, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII, 91532T (23 July 2014); doi: 10.1117/12.2054846
Show Author Affiliations
Kenji Mitsui, National Astronomical Observatory of Japan (Japan)
Tom Nitta, National Astronomical Observatory of Japan (Japan)
Univ. of Tsukuba (Japan)
Norio Okada, National Astronomical Observatory of Japan (Japan)
Yutaro Sekímoto, National Astronomical Observatory of Japan (Japan)
The Univ. of Tokyo (Japan)
Kenichi Karatsu, National Astronomical Observatory of Japan (Japan)
Shigeyuki Sekiguchi, National Astronomical Observatory of Japan (Japan)
The Univ. of Tokyo (Japan)
Masakazu Sekine, National Astronomical Observatory of Japan (Japan)
The Univ. of Tokyo (Japan)
Takashi Noguchi, National Astronomical Observatory of Japan (Japan)


Published in SPIE Proceedings Vol. 9153:
Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII
Wayne S. Holland; Jonas Zmuidzinas, Editor(s)

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