Abstract

Binary optics is a new field combining VLSI and advanced micromachining technology with a computer-generated design of diffractive optical elements to create novel optical devices. Broadband antireflection properties (which have been achieved by gradient-index thin film deposition processes) can be realized using binary optics technology. A design trade-off procedure is developed based on the optical admittance matching theory which provides a graded transition of refractive index between air and the substrate. For this investigation an IR wavelength range of 2-20 µm is considered based on the limitation of 0.5-µm photolithography resolution. Several design samples were used to generate the GDSII stream format for making 10× masks. Silicon wafers with optical apertures as large as 8 × 8 mm were prepared using both direct write electron beam lithography and a deep-UV stepper. Initial data indicate qualitative agreement with predictions. The single level design approximates the ideal moth's eye antireflection structure. More accurate, multilevel processes are presented which predict optimum broadband performance. Design compatibility with VLSI processes makes this technique a good candidate for production of low cost devices for numerous applications; among them are solar cells and detectors. The technique is applicable to the visible range when 0.1-µm resolution becomes available using laser excimer steppers or other means.

© 1989 Optical Society of America