Share Email Print
cover

Proceedings Paper

Binary optics thin-film microlens array
Author(s): M. Edward Motamedi; Robert J. Anderson; R. de la Rosa; Leonard G. Hale; William J. Gunning; Randolph L. Hall; Mohsen Khoshnevisan
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

Binary optics can produce microlenses and lens arrays with theoretical diffraction efficiency as high as 95% for eight-phase level devices. Due to shadowing, mask misalignment, and etching errors that accumulate during fabrication, the actual diffraction efficiency can be reduced to less than 70%. Advances in mask design and e-beam writing have reduced mask misalignment errors to less than 0.2 micrometers but the major issue is the accuracy of the RIE process that is used to transfer a lithographic pattern into the substrate. RIE has two limitations for binary optic applications. First, it cannot be readily employed for the wide range of possible optical substrates of interest (Al2O3 for example), and second, since the pattern is etched directly into the substrate, there is no simple means to calibrate the etch depth during the process. Thin film deposition of the binary structure addresses both of these limitations. It is applicable to a wide range of materials, and accurate in process monitoring of the deposit permits precise control of the feature height. In this paper, we report on eight-phase level binary optic microlenses processed by deposition of SiO2 on fused silica and Al2O3 on sapphire using a projection lithography system. Photoresist processing was achieved by image reversal and lift-off technique. The microlens arrays (in a square format) were designed for (lambda) equals 0.632 micrometers with two microlens sizes of 120 micrometers X 120 micrometers and 240 micrometers X 240 micrometers having speeds of F/12 and F/6 (at the corners), respectively. Optical characterization has demonstrated that the microlens arrays are near diffraction limited and diffraction efficiency is in excess of 80%.

Paper Details

Date Published: 13 January 1993
PDF: 11 pages
Proc. SPIE 1751, Miniature and Micro-Optics: Fabrication and System Applications II, (13 January 1993); doi: 10.1117/12.138890
Show Author Affiliations
M. Edward Motamedi, Rockwell International Science Ctr. (United States)
Robert J. Anderson, Rockwell International Science Ctr. (United States)
R. de la Rosa, Rockwell International Science Ctr. (United States)
Leonard G. Hale, Rockwell International Science Ctr. (United States)
William J. Gunning, Rockwell International Science Ctr. (United States)
Randolph L. Hall, Rockwell International Science Ctr. (United States)
Mohsen Khoshnevisan, Rockwell International Science Ctr. (United States)


Published in SPIE Proceedings Vol. 1751:
Miniature and Micro-Optics: Fabrication and System Applications II
Chandrasekhar Roychoudhuri; Wilfrid B. Veldkamp, Editor(s)

© SPIE. Terms of Use
Back to Top