Experimental studies of 90° light bending by volume hologram: θ-tolerance
| Autor: | Peng, Cheng-Te, 彭成德 |
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| Rok vydání: | 2015 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 In this thesis, a volume holographic concentrator is designed, and its angular tolerance Δθ is improved by holographic multiplexing techniques. We use photopolymer PQ/PMMA as our holographic recording material. Our fabrication process of PQ/PMMA is introduced and its absorption property is characterized by an integrating sphere. Based on the result, proper laser wavelengths are chosen as recording and reconstruction wavelength, and its real-time diffraction efficiency and dark effect are discussed by using 45° transmission recording type. In the 90° recording geometry experiment, we show the effect of bending light to 90° direction by the grating recorded in the material with a high diffraction efficiency about 70%, and we point out the intrinsic problem, small angular tolerance, of using volume holography. We present two different methods to improve the angular tolerance. One is using angular multiplexing technique with two plane waves; the other is using cylindrical wave and plane wave as recording beams. The method of using cylindrical wave as reference wave is chosen due to its more effective way of utilizing material. In order to improve the diffraction efficiency in angular tolerance measurement, we use shift multiplexing technique to increase the effective grating area, and determine optimum conditions, such as exposure process, exposure energy, exposure times, for achieving maximum diffraction efficiency. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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