本論文利用脈衝式Nd：YAG倍頻雷射為激發光源，以研究均向相主客型染料摻雜液晶分子（Guest-host dye doped liquid crystal，GHDDLC）因外加光場所誘發的分子重定向所產生的秩序性以及其鬆弛時間常數。我們發現鬆弛時間常數隨樣品之溫度有關。當溫度遠離相變溫度時，鬆弛時間常數約為數百奈秒；當樣品溫度接近相變溫度時，鬆弛時間常數約1500ns以上。根據藍道的二次相變理論，當液晶接近均向相－液晶相之相變溫度時，分子間的作用力將會增強並且使得非線性效應大幅地增強。分子重定向的鬆弛時間常數與黏滯係數與樣品溫度存在著重要的依存關係，並可由η0*exp(f/T)*(1/T-T*)擬合，η0是黏滯係數，T*是相變溫度。在實驗中我們發現鬆弛時間常數相當符合上述關係式；同樣地，在接近相變溫度時，光誘發的分子重定向所引起的秩序性也有加強的現象。
實驗中同時發現光克爾效應之訊號強度正比於激發光的能量密度；而且當激發光能量密度為1J/cm sq時，光克爾訊號持續時間延緩至10μs以上。光克爾訊號強度也隨著摻雜染
料的濃度而變化。

The laser-induced molecular reorientation effect of guest-host dye-doped liquid crystals in isotropic phase has been studied by measuring the signals of optical Kerr effect using pulsed frequency-doubling Nd:YAG laser as a pumping source. The critical behavior near the isotropic-nematic transition has been observed when the temperature approaches to the phase transition of liquid crystal. The relaxation time constant is about several hundreds of ns as the temperature is far above the clearing point of liquid crystals and that is longer than 1500 ns as the temperature is close to the clearing point of liquid crystals.
According to Landau’s second phase transition theory, the interaction between liquid crystal molecules will be increased and the nonlinearity effect of liquid crystal will be enhanced when the temperature is near the clearing point of liquid crystal. The relaxation time constant of molecular reorientation is a function of viscosity and temperature of liquid crystal, the relationship can be fitted asη0*exp(f/T)*(1/T-T*),where η0 is the viscosity coefficient and T* is the clearing point of the sample.
The optical Kerr signal is found to be proportional to the energy density of pumping source. The optical Kerr signal can be sustained as long as 20μs when the energy density of pumping source reaches to 1J/cm sq. The enhancement of molecular reorientation effect is also observed by increasing the concentration of dye.

總目錄

圖目錄 i
表格目錄 viii
第一章、 簡介 1
1－1研究動機 1
1－2 液晶基礎物理 2
1-3 Dye-Doped Liquid Crystals（DDLC）薄膜簡介 7
1－4論文導覽 …..10
第二章、 原理介紹 11
2－1、隨光場強度倚變之折射率（Intensity-dependent refractive index） 11
2－2、三次磁化率之張量性質（Third-order susceptibility） 14
2－3、光在均向物體中傳播 17
2－4、分子排向（Molecular Orientation）所造成的非線性效應 20
2－5、液晶中雷射誘發之折射率變化機制 25
（一）、分子重定向所產生的秩序度（induced-ordering） ..27
（二）、均向相時分子重定位的動力學 29
（三）、分子結構對均向相重定向的非線性效應之影響 32
2－6、染料分子所增強液晶的非線性效應 34
第三章、 實驗規劃 35
1、樣品之準備 35
（a）、材料介紹 35
（b）、材料的配製 36
（c）、Cell的製作 36
（d）、填充材料 37
2、實驗方法與實驗設置 37
（a）、實驗方法 ..37
（b）、實驗裝置 . .38
（c）、實驗步驟 39
第四章、 實驗結果與數據分析 40
4－1、摻雜染料濃度與樣品溫度對於光克爾訊號強度以及光克爾訊號鬆弛時間常數之影響。 40
a、 光克爾訊號強度以及光克爾訊號鬆弛時間常數對溫度之倚變關係 51
b、 光克爾訊號強度以及光克爾訊號鬆弛時間常數對摻雜染料濃度之倚變關係
. 58
4－2、光克爾訊號強度與光克爾訊號鬆弛時間常數對摻雜染料濃度與與激發光能量密度之倚變關係 61
a、 溫度對光克爾訊號強度以及峰值出現時間之關係 70
b、 光克爾訊號強度對激發光能量密度倚變之關係 81
第五章、 結論 84
未來展望 84
參考文獻 8

1. B. L. Davydov, L. D. Dekacheva, V. V. Dunina, M. E. Zhabotinskii, V. F. Zolin and M. A. Samokhina, JETP Lett. 12, 16 (1970) and Opt. Spectrosc. 30, 274 (1970)
2. T. Kobayashi: IEICE Trans. Electron. 75, 36(1992).
3. Organic Molecules for Nonlinear Optics and Photonics, J. Messier, F. Kajzar and P. Prasad Kluwer Academic Publishers, London, (1991).
4. Special Polymers for Electronics & Optoelectronics, J. A. Chilton and M. T. Goosey Chapman & Hall, London, (1995).
5. Polymers in Optics: Physics, Chemistry, and Applications, R. A.Lessard and W. F. Frank, SPIE, Washington DC, (1996).
6. G. H. Heilmeier, J. A. Castellano and L. A. Zanoni, Proceedings of the International Liquid Crystal Conference, 2-2, 763, New York (1968).
7. T. V. Galstyan, B. Saad and M. M. Denariez-Roberge, J. Chem. Phys. 107, 22, 9319(1997).
8. H. Rau and J. F. Rabek, Photochemistry and Photophysics, 2, 119 (1990).
9. Masahiko Hara, Seiji Ichikawa, Hideo Takezoe and Atsuo Fukuda, Jpn. J. Appl. Phys. 23, 11, 1420(1984).
10. S. S. Gong, D. Christensen and J. Zhang, C. H. Wang, J. Phys. Chem. 91, 17(1987).
11. C. H. Wang and J. L. Xia, J. Phys. Chem. 96, 190(1992).
12. J. L. Xia and C. H. Wang, J. Phys. Chem. 92, 2603(1990).
13. M. Terazima, K. Okamoto and N. Hirota, J. Phys. Chem. 97, 5188(1993).
14. J. C. Bacri, A. Cebers, A. Bourdon, G. Demouchy, B. M. Hegard and R. Perzynski, Phys. Rev. Lett. 74, 5032(1995).
15. G. Heuberger and H. J. Sillescu, J. Phys. Chem. 100, 15255(1996).
16. H. Herbert, W. Urbach and F. Rondelez, J. Chem. Phys. 68, 2725(1978).
17. Massahiko Hara, Hideo Takezoe and Atsuo Fukuda, Jpn. J. Appl. Phys. 25, 12(1986).
18. B. Saad, M. M. Denariez-Roberge and T. V. Galstyan, Optics Let. 23, 9(1998).
19. A. G. Chen and D. J. Brady, Optics Lett. 17, 6(1992).
20. T. V. Gastyan, V. Drnoyan and S. M. Arakelian, Phys. Lett. A 217, 52(1996).
21. I. Janossy, L. Csillag and A. D. Lloyd, Phys. Rev. A 44, 12(1991).
22. I. Janossy, A. D. Lloyd and B. S. Wherrett, Mol. Crys. & Liq. Cryst, 179(1990).
23. L. Marrucci, Mol. Crys. & Liq. Cryst. 321(1998).
24. T. Kosa and I. Janossy, Optics Lett. 20, 11(1995).
25. E. Santamato, G. Abbate, P. Maddalena, L. Marruvvi, D. Papao and E. Maesera, Mol. Crys. &Liq. Cryst. 302(1997).
26. I. Janossy and T. Kosa, Optics Lett. 17, 17(1992).
27. I. C. Khoo, H.Li and Y. Liang, IEEEE Journal of Quantum Electronics 29, 5(1993).
28. H. Li, Y. Liang and I. C. Khoo, Mol. Crys. & Liq. Cryst. 251(1994).
29. L. Szabados, I. Janossy and T. Kosa, Mol. Crys. & Liq. Cryst.
30. Liquid Crystals, I. C. Khoo, Wiley, New York (, 1995).
31. T. Furukawa, T.Yamada, K. Ishikawa, H.Takezoe and A. Fukuda: Appl. Phys. B60 (1995) 485.
32. I. C. Khoo and R. Normandin, IEEE J. Quantum Electron. 21, 2108, 329 (1985)
33. R. Ortler, C. Gr¨auchle, A. Miller and G. Riepl Makromol. Chem. Rapid Commun. 10, 189, (1989).
34. A. G. Chen and D. J. Brady, Opt. Lett. 17, 1231 (1992).
35. A. G. Chen and D. J. Brady Appl. Phys. Lett. 62, 2920 (1993).
36. S. Barkiewicz, A. Januszko, A. Miniewicz and J. Parka, Pure Appl. Opt.5, 799 (1996).
37. F. Simoni, O. Francescangeli, Y. Reznikov and S. Slussarenko, Opt.Lett. 22, 549(1997).
38. S. T. Sun, W. M. Gibbons and P. J. Shannon, Liq. Cryst. 12, 869 (1992).
39. D. B. Taber, J.A.Davis, L. A. Holloway, Jr. and O. Almagor, Appl. Opt. 10, 2623 (1990).
40. T. Ikeda, T. Sasaki and K. Ichimura, Nature 361, 428 (1993).
41. H. Ono and M. Ito, Jpn. J. Appl. Phys. 40, 206 (2001).
42. Andrew J. Lovinger, Karl R. Amundson and Don D. Davis, Chem. Mater. 6, 1726, (1994).
43. Introduction to Modern Optics, Grant R. Fowles, 2nd ed., University of Utah, New York (1975).
44. 現代光學教程,朱自強, 王仕璠, 蘇顯渝, 四川大學出版社, 成都 (1990).
45. Quantum Electronics, A. Yariv, John Wiley & Sons Press, New York (1989).
46. Liquid Crystals-Physical Properties and Nonlinear Optical Phenomena, Iam-Choon Khoo, John Wiley & Sons Press, New York (1995).
47. C. W. Oseen, Trans. Faraday Soc. 29, 83(1933).
48. H. Zocher, Trans. Faraday Soc. 29, 19(1933).
49. Electroopic Effects in Liquid Crystal Materials, L. M. Blinov and V.G. Chigrinov, Springer-Verlag, New York (1994).
50. Liquid Crystals-Applications and Uses, B. Bahadur, Vol.1, World Scientific, Singapore (1990).
51. Nonlinear Optics, Robert W. Boyd, Acadmic Press New York (1992).
52. I.C. Khoo, Mol. Cryst. & Liq. Cryst. 207, 317(1997).
53. L. D. Landau, in Collexted Paper of L. D. Landau, Gordon and Breach, New York, (1965).
54. C. Flytzanis, Y. R. Shen, Phys. Rev. Lett. 33, 14, (1974).
55. P. A. Madden, F. C. Saunders and A. M. Scott, IEEE J. Quantum Elcetron, QE-22, 1287(1986).
56. L. Marrucci, D. Paparo, G. Abbate, E. Santamato, M. Kreuzer, P. Lehnert, T. Vogeler, Phys. Rev. A 58, 6, 4926(1998).
57. K.Geogre, L. Wong and Y. R. Shen, Phys. Rev. Lett. 30, 19 (1973).