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Optical Engineering

Binary Lenses For Use At 10.6 Micrometers
Author(s): Gary J. Swanson; Wilfrid B. Veldkamp
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Paper Abstract

By combining advances in lithography and electromagnetic grating theory, we recently have demonstrated the ability to produce highly efficient binary gratings and binary lenses for use at 10.6 um. Electromagnetic theory predicts that binary gratings with the proper parameters can achieve a first-order diffraction efficiency of nearly 100%. If the periodicity of the grating is on the order of the radiation wavelength, all of the orders become evanescent except for the zero and positive first orders. By choosing the depth-to-period ratio and duty cycle properly, the zero order can be suppressed, placing virtually all of the incident radiation into the first diffracted order. Theoretical calculations have been done only for constant period gratings. However, assuming a lens pattern to be a minor perturbation of a grating, we succeeded in producing an f/5 binary lens with a diffraction efficiency of 96% at 10.6 um. Furthermore, because of the high efficiency of these elements, it becomes practical to consider using more than a single diffractive element in a system. We have constructed a simple afocal telescope from two binary lenses. The telescope has a 2 in. entrance aperture and a magnification of 5. A final point to be considered is the wavefront quality of these elements. Electron beam machines, which are used to write the lens patterns, are designed to draw the pattern in a raster fashion. This quantization sets a limit on the quality of the lens pattern.

Paper Details

Date Published: 1 August 1985
PDF: 5 pages
Opt. Eng. 24(5) doi: 10.1117/12.7973576
Published in: Optical Engineering Volume 24, Issue 5
Show Author Affiliations
Gary J. Swanson, Massachusetts Institute of Technology (United States)
Wilfrid B. Veldkamp, Massachusetts Institute of Technology (United States)


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