Diffractive Optical Elements: Fabrication, Replication, and Applications and Optical Properties of a Visual Field Test

Abstract: This thesis mainly treats the fabrication, replication and applications of diffractive optical elements. A smaller part deals with optical properties of a visual field test.

Diffractive optical elements are computer-generated micro-optic components that use diffraction to manipulate light. These novel optical elements are characterized by high efficiency, design flexibility, light weight and small size. Furthermore, they can be replicated at low cost for mass production. These properties give diffractive optical elements the potential to become key components in future optical systems.

In the first part of this thesis, the technical limitations of direct-write electron beam lithography for diffractive optics fabrication are studied. The electron beam can readily be focused to a spot size of less than 100 nm, but scattering of the exposing electrons within a resist layer results in a broadening of the exposing beam and a loss in resolution - the proximity effect. We measured and modeled this effect. We presented a practical way to compensate partly for the electron scattering and demonstrated successfully manufactured proximity-compensated elements. We also showed how the relief depths of exposed structures can be optimized by repeated development.

We studied the feasibility and fidelity of replicating diffractive structures by compact disc injection molding equipment. A method for replicating diffractive elements into fused silica was proposed and investigated.

A diffractive beam homogenizer, based on a novel design, was fabricated and evaluated together with an excimer laser. A diffractive axicon was designed and fabricated for use in a laser-induced detection system. In an initial study we proposed and investigated a novel scheme for fabricating diffractive elements with inherent antireflection properties.

One method for visual field testing is high-pass resolution perimetry. Properties of this method were studied using both optical analytical techniques and measurements in normal humans.