Thermal fixing of volume holograms in LiNbO3 crystals

• Main Authors: Chao-Ray Hsieh, 謝兆瑞
• Other Authors: Ken-Yuh Hsu
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/66208617464538753948

碩士 === 國立交通大學 === 光電工程所 === 87 === In this thesis, we investigate the thermal fixing techniques of volume holographic storage in LiNbO3 crystals. We have performed theoretical modeling, computer simulations, and optical experiments. First, we incorporate ionic transport equations into the Kukhtarev''s equations for photorefractive crystals. Then by using the linear approximation method, we have developed a theoretical model for thermal fixing under both short-circuit condition and open-circuit conditions on crystals. The temperature transition effect during the heating and cooling processes have been taken into account in our theoretical model. We have considered two processes of the thermal fixing: one is recording at low temperature, compensating at high temperature, and then developing at low temperature, so-called the L-H-L process. The other one is recording at high temperature, and then developing at low temperature, so-called the H-L process. Our calculations show that the compensation time and temperature are two key points of thermal fixing. In order to achieve optimal diffraction efficiency for a given material parameters, we could first choose a suitable compensation time and then the corresponding compensation temperature can be obtained. On the other hand, for the H-L process, there exists an optimal recording temperature for a given material parameters. Therefore, we should first find the recording temperature, and then the corresponding recording time can be obtained. Furthermore, we have also studied the effects of material parameters and the recording angles on thermal fixing. During this investigation we have performed optical experiment. The results show a coincidence with the simulation results. Our studies provide a useful guide for designing the thermal fixing procedures of holographic storage.