本論文主要研究摻雜偶氮染料的液晶薄膜在偏振光柵下引致的光折變效應, 其乃由兩道同調且正交的圓偏振激發光場及外加直流電壓同時存在所引致。能夠在偏振光柵下成功的引致光折變效應，是由於偶氮材料具有二色性的關係。光折變效應會導致雙光耦合的現象，本篇論文主要是研究雙光耦合的強度與外加電壓，光強比例，以及總能的關係。
實驗結果,有四個結論;其一:電壓打開時，雙光耦合的現象即產生，電壓關閉時，雙光耦合的現象即消失。其二: 雙光束耦合增益係數與雙束激發光光強比例的關係, 激發光光強比例為給光的那道光能量除以得到光的那道光能量，當激發光光強度比例愈大，則耦合增益係數愈大。其三:耦合增益係數與外加電壓的關係，當外加電壓過小或過大，其耦合增益係數皆會變小。其四，耦合增益係數與總激發光能的關係，當總能過大或過小，都會有較小的耦合增益係數，因此發現，耦合增益係數也與總能有關。

This thesis studies the orientational photorefractive (PR) effect induced by a polarization grating (PG) in an azo-dye-doped liquid crystal (ADDLC) film. The PG-PR effect is induced by applying a dc field together with an interfering field created by two mutually orthogonal circularly polarized beams simultaneously. The cause of the PG-PR effect is due to the anisotropy of azo-dye to the polarization of a pump beam. Two-beam coupling(TBC) is one featured result from orientational photorefractive (PR) effect. In this thesis, we study how the applied voltage, beam power ratio and total pump beam intensity effect the gain constant in the TBC effect.

Four conclusions can be drawn from the experimental results.
(1) When the applied dc voltage is on(off), the TBC effect shows up(off).
(2) The power ratio of the two pump beams affects the TBC effects significantly. It is found that the coupling gain constant increasing with the power ratio.
(3) The coupling gain constant is initial increasing with the magnitude of the applied voltage. It is peaked at ~2.6V, and then decreasing with further increase of the voltage.
(4) The total pump-beam intensity is found to affect the coupling gain constant effectively. Similarly to above(3), it is increasing with the total pump-beam intensity, and peaks at ~44.8mW/cm2, and finally decreases with further increase of the pump-beam intensity.

參考文獻(References)
1. E. V. Rudenko and A. V. Sukhov , JETP. 78, 875(1994)
2. I. C. Khoo , H. Li , and Y. Liang , Opt. Lett. 19, 1723(1994)
3. I. C. Khoo , Opt. Lett. 20, 2137(1995)
4. I. C. Khoo , IEEE J. Quant. Electron. 32,525(1996)
5. I. Janossy , T. Kosa , Opt. Lett. 17, 1182(1992)
6. F. Simoni and O. Francescangeli , J. Phys: Condensed. Matter. 11, R439(1999)
7. Photorefractive effect induced by polarization grating in an azo-dye-doped nematic liquid crystal film(成功大學 王君瑞)
8. T. Tskada , “TFT/LCD Liquid-Crystals Displays Addressed by Thin-Film Transistor” , Jordon and Breach , Tokyo , Japan(1996), Chap. 6
9. P. Yeh and C. Gu , “Optics of Liquid Crystal Display” , Wiley , New York(1999)
10. E. B. Priestley , P. J. Wojtowicz and P. Sheng , “Introduction to Liquid Crystals” , Princeton , New Jersey(1975), Chap. 1 , Chap. 8.
11. S. Chandrasehker , F. R. S.,“Liquid Crystals“ , Second edition, Cambridge University Press, Cambrideg(1992), Chap. 1, Chap. 3.
12. I. C. Khoo , S. T. Wu , “Optics and Nonlinear Optics of Liquid Crystals” , World Scientific(1993)，Chap. 2.
13. A. Yariv , “Optical Electronics in Modern Communications” , Oxford University Press, New York,(1997), Fifth edition , Chap.1.
14. A.Yariv , “Quantum Electronics” Wiley, New York,(1998), Third edition, Chap. 5.
15. I. C. Khoo , S. T. Wu , “Optics and Nonlinear Optics of Liquid Crystals” World Scientific(1993), Chap. 2.
16. Peter J. Collings and Michael Hird , “Introduction to Liquid Crystals Chemistry and Physics” , Taylor and Francis(1997), Chap.10
17. P. C. Mehta and V. V. Rampal , “Lasers and Holography” , World Scientific, Singapore(1993), Chap. 4
18. P. Hariharan, “Optical Holography-Principles , Techniques and Applications” , Cambridge University Press, Cambridge(1984), Chap. 2
19. P. K. Rastogi , “Holographic Interferometry” , Springer-Verlag , Berlin(1985), Chap. 2
20. E. Hecht,“Optics“, Addison Wesley Longman, Inc(1997), Third editon, Chap. 13.
21. H. J. Eichler , P. Gunter and D. W. Pohl,“Laser-Induced Dynamic Gratings“, Springer-Verlag , Berlin,(1985), Chap. 2.
22. N. K. Viswanathan, S. Balasubramanian , L. Li, S. K. Tripathy and J. Kumar, Jpn. Appl. Phys. 38, 5928(1999)
23. P. Yeh , “Introduction to Photorefractive Nonlinear Optics”, Wiley , New York (1993), Chap. 2, Chap, 3, Chap. 4
24. F. Simoni and O. Francescangeli , J. Phys : Condensed . Matter. 11, R439(1999)
25. B. Bahadur, ‘Liquid Crystal –Applications and Uses’, World Scientific Press, Singarpore(1992), Vol. 3
26. S. Bartkiewicz , A. Miniewicz , A. Januszko , and J. Parka, Pure Appl. Opt. 5, 799(1996)
27. Ki Hyun Kim, Eun Ju Kim, Sang Jo Lee, Jung Hoon Lee, and Chong Hoon Kwak，applied physics letters, 85, 366(2004)