ABSTRACT
Microoptical Structures .................................................................................. 52 2.6 Etching Microoptics in Other Materials of Interest for the Optical
Spectrum GaN, SiC, and Al2O3....................................................................... 55 2.7 Etch Processing II-VI Materials ZnSe and Multispectral ZnS ....................... 62
2.7.1 Applications for Optical Components in ZnSe and ZnS ....................66 2.8 Etching Alternative Materials for IR Applications-IR Glass (IG6) .............. 71
2.8.1 Etching Process Development for IG6 ............................................... 74 2.9 Etching Microoptics in an Optical Material That Is Not Reactive .................. 75
2.9.1 Gray-Scale Fabrication of Gaussian Homogenizer and MLA ............ 76 Acknowledgments .................................................................................................... 79 References ................................................................................................................ 79
This chapter presents and reviews etching techniques for microoptics fabrication that were developed at both MEMS Optical, Inc. and related companies during the past 16 years. Many practical examples and applications are presented. The principal method of fabricating microoptics at MEMS Optical has been using gray-scale photolithography for patterning and plasma etching for transferring the pattern into a substrate. The gray-scale manufacturing technique has allowed fabrication of a wide range of microoptical devices for use in a broad range of applications. The photolithographic patterning method and etch pattern transferal techniques can be used in the manufacture of both diffractive and refractive microoptical devices. Some of the more commonly manufactured microoptical elements include beam splitting
diffractive optics, beam shaping diffractive optics, diffusing or homogenizing diffractive optics, diffractive lenses and lens arrays, refractive microlenses and microlens arrays (MLAs), and other phase-modulating optics. The functional microoptics have been produced in a wide range of substrate materials for addressing applications across the electromagnetic spectrum. Microoptics have been fabricated for use across the optical radiation spectrum that ranges from deep ultraviolet (DUV) at the wavelength of 157 nm through long-wave infrared (LWIR) at the wavelength of 14 μm. Microoptics have been fabricated into many substrate materials that have transmission bands within the optical spectrum including fused silica, silicon, germanium, gallium phosphide (GaP), gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide, Pyrex, borosilicate glasses, high refractive index optical glasses, fl at panel display glasses such as C-1737 and Eagle2000, zinc selenide (ZnSe), multispectral zinc sulfi de (ZnS), sapphire, and calcium fl uoride. Some of the high index glasses and materials investigated were OHARA S-TIH-53, OHARA S-LAH79, and Schott SF57. The chapter describes the fundamental steps in manufacturing microoptics with an overview of the gray-scale photolithography required to produce the threedimensionally patterned microoptic structures in a variety of material systems.
