全像多工技術於體積全像集光元件之設計與改善研究

Abstract

本論文主要研究方向為利用體積全像與全像多工技術，設計製作體積全像集光元件並改善其角度容忍度，以期有效收集與控制太陽光的方向，用於太陽能之集光元件。 我們使用自行製備的感光高分子PQ/PMMA作為記錄材料，首先介紹材料的製備流程以及進行其吸收光譜的量測，選擇適當的記錄與讀取光源，並利用45°穿透式全像記錄架構，探討材料的即時繞射效率變化與暗反應機制。接著在90°全像記錄系統中，展示全像集光器的初步概念，呈現材料將光轉折90°的效果，具有高效率約70%，並指出體積全像存在的角度容忍度的問題。在本研究中，我們提出兩種改善角度容忍度的解決方法，ㄧ為利用兩道平面波進行角度多工記錄，另一則為使用柱狀波與平面波作為記錄光，將兩者進行比較後，選擇以柱狀波作為參考波進行全像記錄，一次性的將不同週期與方向的光柵記錄到材料裡，再配合位移多工技術，探討其記錄的流程、曝光能量、曝光次數，找到最佳的曝光條件，以提高整體的繞射效率。

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.