Search

The fabrication of near-micrometer-sized close-packed coherent microlens arrays on spheric or aspheric surfaces has been accomplished by use of a compact holographic projector system that was developed for producing multimicrometer down to submicrometer grid patterning on curved surfaces. The microlens arrays, which can be utilized as moth-eye relief structures, are formed in a photoimageable bisbenzocyclobutene polymeric resin by a photolytic process involving standing-wave interference patterns from the holographic projector system. Because of absorption, each integral microlenslet of the finished arrays possesses a near-paraboloid contour. The trajectories of the meridional rays from each microlenslet can be optimized to intersect at either a single point or a locus of points.

A compact holographic projector system was built and tested. This projection system offers a practical approach for making a highly corrected mesh or grid pattern on curved surfaces. The pattern can range in size from multimicrometer to submicrometer dimensions and be recorded in either positive or negative photoresist. Standing-wave interference patterns in the form of a diverging close-packed lattice of either hexagonal or square rodlike intensity maxima extending outward from a point or a locus of points are produced by multiple-beam holography that involves the combination of a holographic diffraction grating and a hypercomatic focusing objective.

We describe the development and testing of a holographic projection system that is used to produce micro-optical devices. The projector uses a two-dimensional two-phase-level diffraction grating to produce multiple coherent beams and an interferometric optical system behind the grating to recombine the beams to produce interference patterns that have been recorded within a photosensitive substrate. The two different substrates that we used are a diazo imaging material and a bisbenzocyclobutene (BCB) polymeric resin for fabrication of surface relief microstructures. After the exposed photosensitive substrate is developed, the recorded interference pattern forms a micro-optical device. The analysis and testing of these micro-optical devices show promise that this technique can form patterns uniformly over a region of several centimeters in diameter on flat or curved substrates. The experimental testing results of these micro-optical devices demonstrate that this method is a simple and energy efficient system to produce microstructures compared with other methods. These devices may be used as a new generation of directional light filters or monolithic microlenslet arrays that may have applications in communications, display, and components technologies.