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1.3 PHYSICAL SCIENCES, Optics, Polymer science
Holography is a firmly established discipline that can be used as a tool for scientific and engineering studies and as a display medium as well. Until now both silver halide photographic emulsions (SHPE) and dichromated gelatine (DCG) have been the most common materials used for high efficiency full colour reflection hologram recording. However, these materials require wet chemical processing for developing the holograms which is laborious and costly from the point of view of commercial applications. Self-developing photopolymers such as acrylamide based photopolymer (ABP) which do not require development are the ideal choice for real-time recording and reconstruction of holograms. This thesis reports on the development of an acrylamide based photopolymer system for full colour reflection holographic display. Firstly ABP was dye sensitised separately at 633 nm and 473 nm using methyleneblue and acriflavine respectively to record holographic reflection gratings and the corresponding diffraction efficiencies were measured. Following this, the ABP material which had already been sensitised at 532 nm at the IEO centre by using erythrosine B as a dye, a panchromatic ABP was developed at IEO sensitised at all three selected primary wavelengths which were available, namely 633 nm, 473 nm and 532 nm. The Bidirectional Scattering Distribution Function (BSDF) was measured for the ABP and scattering obtained was relatively low compared with that of air and glass in the visible region. Reflection holographic gratings were recorded at 633 nm, 532 nm, and 473 nm wavelengths to evaluate the diffraction efficiencies at spatial frequencies of 4200 lineslmm, 5000 lineslmm and 5700 lineslmm respectively. An optical setup was established to record multicolour holograms by combining three selected laser beams (at 633 nm, 532 nm, and 473 nm). Further multicolour reflection holographic gratings were recorded using a combined single RGB beam so that all wavelengths illuminated the same spot. Spectral characterisation was carried out on the multicolour reflection holographic gratings and the Bragg peaks of the diffracted beam were monitored and compared with the recording wavelengths to reveal the shifts which were considered due to the dimensional changes inside the photopolymer. These spectral shifts in the photopolymer response were minimised by using zeolite nanoparticles (Si-MFI 30nm). Reflection holograms of objects were successfully recorded at all three primary wavelengths, and also using a combined RGB beam. The results provided a strong confirmation that this acrylamide based photopolymer can be used as a panchromatic recording material and can be employed in future commercial holographic applications.
Meka, C.: Development of Acrylamide Based Photopolymer for Full Colour Display Holography. Doctoral Thesis. Dublin Institute of Technology, 2010.