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Silicon Fresnel lens fabricated using greyscale lithography
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Paper Abstract

A silicon Fresnel lens was designed and fabricated using a greyscale lithography technique to shape optical emissions from an edge-emitting semiconductor diode laser. The laser beam was collimated in the fast axis and allowed a ±3° divergence in the slow axis along with bias angle accomplished through lens decentering. The lens had an aperture of 6.8 mm × 2.2 mm and 1 mm in total thickness. The lens was first designed as a contiguous surface using conventional raytracing methods, and then converted to a Fresnel sag model with an etch depth of 6.25 micrometers. The sag model along with the manufacturing tolerances were fed back through numerical tools to refine the design and modify the lens shape and laser position. Optical profilometry of fabricated lens element found deviations from design and nonuniformity across the entire aperture, with over-etching in the center and under-etching toward the edge of the lens. Characterization of the fabricated lenses showed less than 5% deviation in etch depth. Collimation performance was measured to be less than 2 milliradians, which was in close agreement with design models. Greyscale fabrication of the lens element enabled complex curvatures to be combined and provided a compact solution for direct, single optic coupling of diode laser to free-space projection.

Paper Details

Date Published: 30 August 2019
PDF: 10 pages
Proc. SPIE 11104, Current Developments in Lens Design and Optical Engineering XX, 111040G (30 August 2019); doi: 10.1117/12.2530649
Show Author Affiliations
Cheng-Po Chen, GE Global Research (United States)
Jason Karp, GE Global Research (United States)
Tim Toepfer, GE Global Research (United States)
Oliver Boomhower, GE Global Research (United States)
Jim Kretchmer, GE Global Research (United States)
Shubhodeep Goswami, GE Global Research (United States)
Sachin Dekate, GE Global Research (United States)
Loucas Tsakalakos, GE Global Research (United States)


Published in SPIE Proceedings Vol. 11104:
Current Developments in Lens Design and Optical Engineering XX
R. Barry Johnson; Virendra N. Mahajan; Simon Thibault, Editor(s)

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