| Summary: | 碩士 === 國立成功大學 === 光電科學與工程研究所 === 98 === This thesis studies the electro-optical characteristics of the polymer-dispersed liquid crystals (PDLCs) polymerized using off-resonant light. The materials and technique are then applied to fabricate holographic amplitude gratings (HAG). The key concept is based on the low absorbance of the polymerization light. Restated, the incident polymerization light (off-resonant light) cannot be strongly absorbed by the used photo-initiator dyes near the incident surface. Accordingly, it can penetrate the PDLC sample, and is uniformly absorbed across the cell, and thus, produces uniform PDLC structures.
Notably, the contrast between the high-intensity scattered regions (scattered regions) and the low-intensity regions (transparent regions) are sharp in the fabricated holographic amplitude gratings. Moreover, the concentration of the monomer (DPPA) is one of the keys to optimize the holographic amplitude gratings. Experimentally, it is found that the optimum concentration of monomer in the sample compound is ~19 wt%. It gives the maximum and final diffraction efficiencies. This approach can be used to fabricate 2-dimension holographic gratings. Experimentally, the fabricated 1-D and 2-D holographic amplitude gratings are electrically switchable and polarization independent. In addition, it is experimentally demonstrated that the diffraction efficiency, the stability and the contrast of the gratings fabricated using off-resonant polymerization process are much better than those produced by resonant light.
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