Holographic Optical Elements with Electro-optic Control

Michael Leigh Ermold

doi:10.17918/etd-6020

Although polymeric and liquid crystalline materials have been separately studied for many years, optical devices based the interaction between these two materials in a composite device have come to the forefront of technology in recent years. Liquid crystals typically have strong interactions with the surfaces with which they make contact, with the dominant effects arising from geometrical and chemical contributions. It is this surface interaction that allows the construction of thin, flat liquid crystal displays that now can be found in almost every type of portable electronic device requiring information display. Instead of the liquid crystals lying on a polymer surface, they can be embedded within a thin film. In this format, the liquid crystal will assume the shape of ellipsoidal cavities, forming the so-called polymer dispersed liquid crystals. The index mismatch between the liquid crystal and the surrounding polymer matrix creates a highly efficient scattering device. This index mismatch can be modulated by applied electric fields, facilitating electronic grayscale control of the scattering efficiency. With a sufficiently high applied field, the device can be made transparent. Utilizing the holographic techniques developed by Gabor, Leith, and Upatnieks, polymer dispersed liquid crystals can be formed under holographic conditions to produce holographic polymer dispersed liquid crystals (H-PDLC). The resulting stratified structure is composed of layers of hardened polymer separated by layers of liquid crystal droplet-rich planes. Optical structures in this form also possess the same electro-optic properties as their unstructured predecessors. A whole host of diffractive optical devices can be created via holographic means, which includes, but is not limited to transmission gratings, reflection gratings, 2D and 3D photonic crystals and holographic optical elements. In this work, I have examined the role of H-PLDC gratings that function as holographic focusing mirrors from a theoretical and experimental perspective. Presented here are methods of formation, their optical and electro-optic properties, the device morphology and its relation to the observed properties, and a theoretical model for the have also been observed through the use of optical measurements, optical and electron imaging. I will also discuss implications when HOEs are used in imaging and non-imaging applications.

Holographic Optical Elements with Electro-optic Control

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Holographic Optical Elements with Electro-optic Control

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