Flexible refractive and diffractive micro-optical films shaped by fitting aspherical microprofiles with featured aperture and depth and their spatial arrangement for imaging applications

Abstract

Patterned surface microstructures over a common silicon wafer are constructed by a single-mask ultraviolet (UV) photolithography and a dual-step wet potassium hydroxide etching. Oriented surface contours such as aspherical refractive profiles, diffractive phase steps, or even the composite appearance shaped by combining both refractive and diffractive microprofiles can be accurately predicted and finely configured through computational fitting. This critical operation involves a careful adjustment of the location of silicon microholes with suitable apertures and concave depths so as to outline a needed square microwindow map defined by the single-mask UV photolithography. This approach leads to an aspherical surface or phase steps with required roughness based on a greedy algorithm developed in-house. The obtained micro-optical films can be effectively used to transform common laser beams with a typical Gaussian profile into patterned beams with various complicated wavefronts. The proposed method highlights a low-cost development of adaptive optical imaging by constructing relatively complicated wavefront or objective circumstances for quantitatively evaluating imaging efficiency. The technology should find typical applications in antilaser interference or attack imaging.