GRAY-SCALE MASKS FOR DIFFRACTIVE-OPTICS FABRICATION .1. COMMERCIAL SLIDE IMAGERS

Fabrication of diffractive optics with binary masks requires multiple photolithographic processes to produce high-efficiency elements. Align ment or etching errors at any stage of fabrication decrease the effici ency of the element. We developed an easily accessible procedure that reduces fabrication complexity and costs by using a single gray-scale mask. The gray-scale patterns are generated by commercial slide imager s and are then photoreduced onto low-contrast film plates. Multiple-le vel or continuous relief structures (kinoforms) may be constructed by use of the photoreduced gray-scale patterns as lithographic masks. Dif fractive-optic lenses and blazed gratings were fabricated in photoresi st with this procedure. First-order diffraction efficiencies as high a s 85% were measured for the blazed gratings. The advantages and the li mitations of this technique are discussed.