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1 November 1991 Silicon microlenses for enhanced optical coupling to silicon focal planes
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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.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
M. Edward Motamedi, Marsden P. Griswold, and Robert E. Knowlden "Silicon microlenses for enhanced optical coupling to silicon focal planes", Proc. SPIE 1544, Miniature and Micro-Optics: Fabrication and System Applications, (1 November 1991);


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