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Proceedings Paper

Silicon microlenses for enhanced optical coupling to silicon focal planes
Author(s): M. Edward Motamedi; Marsden P. Griswold; Robert E. Knowlden
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Paper Abstract

The microlens array reported in this paper is for enhanced optical coupling of near IR photons into the edges of the Rockwell solid-state photomultiplier (SSPM). Here the edge-illumination is necessary to achieve the required quantum efficiency of near IR photons in the SSPM, a device which is capable of photon counting. SSPM detection requires a method of highly efficient optical coupling to the gain medium to concentrate light with a 100 fill factor where lenslets are centered with a precise 0.2 micrometers accuracy. The microlens array is designed for a center wavelength of 1.3 micrometers , 1975 micrometers pixel dimension and a speed of f/4, which results in the array being nearly diffraction limited. The smallest feature size is 0.9 micrometers for the 8-phase level devices. From this design, we have successfully fabricated an 8-phase- level SSPM microlens array which demonstrates a 0.2 micrometers alignment accuracy among all three mask levels. SEM studies of the microlens show a high-quality surface finish and near vertical sidewalls. Optical characterization demonstrates that the microlens array is diffraction- limited at the design speed and design wavelength, with diffraction efficiency higher than 84.

Paper Details

Date Published: 1 November 1991
PDF: 11 pages
Proc. SPIE 1544, Miniature and Micro-Optics: Fabrication and System Applications, (1 November 1991); doi: 10.1117/12.49370
Show Author Affiliations
M. Edward Motamedi, Rockwell International Science Ctr. (United States)
Marsden P. Griswold, Lincoln Lab./MIT (United States)
Robert E. Knowlden, Lincoln Lab./MIT (United States)


Published in SPIE Proceedings Vol. 1544:
Miniature and Micro-Optics: Fabrication and System Applications
Chandrasekhar Roychoudhuri; Wilfrid B. Veldkamp, Editor(s)

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