本論文的研究題目為「光敏材料於液晶的研究與其在光子元件之應用」，共有四個主題。這四個主題所研究的對象可以分為兩類: 一為摻雜染料之液晶盒，另一為摻雜富勒烯之聚乙烯咔唑的光導體，描述如下:

(1) 於摻雜偶氮染料液晶盒中，利用一道未經過檢偏器之穿透光量測染料吸附薄膜表面的光散射程度。藉由光的散射程度可以觀察到染料引致之波紋結構的形成，並且同時量測液晶導軸的重新定位可獲得此結構的錨定力。當波紋結構逐漸地被形成時，光散射的程度減少，使得光偵測器接收到較高的光能量。這是因為波紋的尺度在量測光的波長內，所以散射光由瑞立散射(Rayleigh scattering)轉為米式散射(Mie scattering)。因此可以藉由光散射的程度監控染料引致之波紋結構的形成。

(2) 利用電容方法計算摻雜偶氮染料之液晶盒的極方位錨定能量。當此液晶盒受到激發光的照射下，基板的錨定能量(7.90*10-6 J/m2)包含了兩部分:染料吸附引致的錨定能量(5.74*10-6 J/m2)以及預先存在於玻璃基板上之染料所引致的錨定能量(2.16*10-6 J/m2)。後者歸因於在未受光照射前分佈於基板上的染料，會在激發光照射下引致力矩而造成基板極方位錨定能量的產生。當此液晶盒經過激發光的照射後，吸附所引致的錨定能量仍然存在於基板上，而預先存在於玻璃基板上之染料所引致的錨定能量則會消失。吸附所引致的錨定能量屬於弱錨定，因此影響了此液晶盒的下降時間與閥值電壓。此外，利用這些錨定能能夠繪製液晶分子於此液晶盒中極角度的分布，這個分布驗證了此液晶盒的電容變化。

(3) 利用單邊水平配向的摻雜偶氮染料之液晶盒以及線性光衰減片製作光學元件:線性偏振轉動器。此元件的製作是基於激發光強度對吸附所引致扭轉角的線性控制：高(低)光強度造成大(小)的扭轉角。因此，照射面上的液晶導軸會被光配向而形成連續90度的扭轉，而液晶盒內的導軸會從水平排列形成90度扭轉排列。這個元件能夠轉動線性偏振輸入光的偏振，轉動的程度會和輸入光的入射的位置有關。這個線性偏振轉動器具有大的連續扭轉區域(~5.6 mm)以及高對比度(~1000:1)。

(4) 利用垂直配向的高分子穩定液晶(polymer-stabilized liquid crystals)開發全光控且偏振無關的空間濾波器。元件的製作是基於光對光導體薄膜的效應:高(低)強度的光使得光導電薄膜具有高(低)的電導率，這個效應讓具有光導體薄膜的高分子穩定液晶盒有較低(高)的閥值電壓。實驗結果指出這個光學元件是屬於高通濾波器，而且其在光學傅立葉轉換系統下具有低的光功率(1.11 mW/cm2)消耗。 此外，這個空間濾波器的高通特性可以藉由相關的理論得到驗證。因此，這個全光控且偏振無關的空間濾波器可以用來強化影像的邊緣。

This paper entitled “Study of photosensitive materials with/in liquid crystals and their applications in photonic devices”, having four topics. The four topics are described as the following:

(1) The first topic in this paper is “Dynamics of photoalignment in dye-doped Liquid crystals.” A transmitted light without analyzer was led into the pump-probe twist nematic experiment in dye-doped liquid crystals to observe the light scattering from the dye-adsorbed surface during photoalignment. The morphology of the dye-absorbed surface monitored by this transmitted light is correlated with the formation of the ripple structure, which is reflected by the anchoring of the dye-adsorbed layer, which is in turn revealed by measuring of the surface director reorientation angle throughout the process. As the regular ripple structure is gradually formed, Rayleigh scattering is transferred to Mie scattering since the scale of the ripple structure is at the wavelength.

(2) The second topic is “Determination of polar anchoring energy of dye-doped liquid crystals by measuring capacitance.” Polar anchoring energy of a dye-doped liquid crystal (DDLC) cell is determined based on capacity measurements. Experimental results indicate that under the illumination of a pump beam, the polar anchoring energy (7.90*10-6 J/m2) includes the adsorption-induced anchoring energy (5.74*10-6 J/m2) and the preexisting-dye-induced anchoring energy (2.16*10-6 J/m2). The latter is attributed to the torque, which is induced by the dye molecules on the boundary surface even before illumination. After the illumination, the adsorption-induced anchoring energy remains and the preexisting-dye-induced anchoring energy disappears, with the former revealing that weak anchoring affects the decay time and threshold voltage of the DDLC cell. Moreover, plotting the polar angle distributions in the DDLC cell reveals its correlation with variations in the capacitance of the DDLC cell.

(3) The third topic is “Linear polarization rotators based on dye-doped liquid crystal cells.” Linear polarization rotator is fabricated by a single-side homogenously-aligned dye-doped liquid crystal cell and linear variable neutral density filter (LVNDF). When a pump beam passing through the transmittance-linear region of LVNDF irradiates on the untreated surface, the surface LC director in the irradiation region is photoaligned into a continuous twist from 0o to 90o. Consequently, the bulk director gradually transits from a homogeneous to twist orientation. This device is capable of rotating the polarization of an input linearly polarized light depending on the beam position, exhibiting a large continuous twist region (~5.6 mm) and high contrast ratio (~1000:1).

(4) The four topic is “All-optical and polarization-independent spatial filter based on a vertically-aligned polymer-stabilized liquid crystal film with a photoconductive Layer.” An all-optical and polarization-independent spatial filter was developed in a vertically-aligned (VA) polymer-stabilized liquid crystal (PSLC) film with a photoconductive (PC) layer. This spatial filter is based on the effect of light on the conductivity of PC layer: high (low)-intensity light makes the conductivity of the PC layer high (low), resulting in a low (high) threshold voltage of the PC-coated VA PSLC cell. Experimental results indicate that this spatial filter is a high-pass filter with low optical-power consumption (about 1.11 mW/cm2) in an optical Fourier transform system. The high-pass characteristic was confirmed by simulation. Accordingly, the high-pass spatial filter can be used to enhance the edges of images.

[1] F. Simoni, Nonlinear Optical Properties of Liquid Crystals and Polymer Dispersed Liquid Crystals (World Scientific, Singapore, 1997).
[2] P. G. de Gennes and J. Prost, The Physics of Liquid Crystals (Oxford University Press, New York, 1993).
[3] I. C. Khoo, Liquid Crystals: Physical Properties and Nonlinear Optical Phenomena (John Wiley & Sons, New York, 1995).
[4] G. Barbero and L. R. Evangelista, An Elementary Course on the Continuum Theory for Nematic Liquid Crystals (World Scientific, Singapore, 2000).
[5] H. Ono and N. Kawatsuki, and J. Nonlinear Opt. Phys. & Mater. 8, 329 (1999).
[6] I. Jánossy, Phys, Rev. E 49, 2957 (1994).
[7] L. Marrucci, Mol. Cryst. Liq. Cryst. 321, 57 (1998).
[8] F. Simoni and O. Francescangeli, J. Phys: Condensed. Matter. 11, R439 (1999).
[9] T. Ikeda, J. Mater. Chem. 13, 2037 (2003).
[10] L. M. Blinov, M. I. Barnik, A. Mazzulla, and C. Umeton, Mol. Mater. 5, 237 (1995).
[11] T. Ya. Marusii, Yu. A. Reznikov, and S. Slussarenko, Mol. Mater. 6, 163 (1996).
[12] D. Voloshchenko, A. Khyzhnyak, Y. Reznikov, and V. Reshetnyak, Jpn. J. Appl. Phys. 34, 566 (1995).
[13] C. R. Lee, T. L. Fu, K. T. Cheng, T. S. Mo, and Andy Y. G. Fuh, Phys. Rev. E 69, 031704 (2004).
[14] S. Serak, A. Kovalev, A. Agashkov, H.F. Gleeson, S.J. Watson, V. Reshetnyak, and O. Yaroshchuk, Opt. Commun. 187, 235 (2001).
[15] O. Francescangeli, D. E. Lucchetta, S. S. Slussarenko, Y. A. Reznikov, and F. Simoni, Mol. Cryst. Liq. Cryst. 360, 193 (2001).
[16] Andy Y. G. Fuh, C. C. Liao, K. C. Hsu, C. L. Lu, and C. Y. Tsai, Opt. Lett. 26, 1767 (2001).
[17] T. H. Lin and Andy Y. G. Fuh, Opt. Lett. 30, 1390 (2005).
[18] T. H. Lin, Yuhua Huang, Andy Y. G. Fuh, and Shin-Tson Wu, Opt. Express 14, 2359 (2006)
[19] O. B. Pantaleon, R. P. Aguilar, A. S. Castillo, J. C. Ramirez-San-Juan, R. R. Garcia and E. A. Gonzalez, Mol. Cryst. Liq. Cryst. 488, 1 (2008).
[20] http://www.chemyq.com/En/xz/xz1/1846fiqdc.htm
[21] Y. Wang, Nature 356, 585 (1992).
[22] A. G. Jepsen, D. Wright, B. Smith, M. S. Bratcher, M. S. DeClue, J. S. Siegel, and W. E. Moerner, Chem. Phys. Lett. 291, 553 (1998).
[23] J. Qian, C. Xu, S. Qian, and W. Peng, Chem. Phys. Lett. 257, 563 (1996).
[24] E. Hecht, Optics, 4th ed. (Addison Wesley, San
Francisco, 2002).
[25] A. Yariv, Optical Electronics in Modern Communications, 5th ed. (Oxford University Press, New York, 1997).
[26] V. G. Chigrinov, V. M. Kozenkov, and H. S. Kwok, Photoalignment of Liquid Crystalline Materials: Physics and Applications (Wiley, New York, 2008).
[27] M. Jiao, Z. Ge, Q. Song, and S. T. Wu, Appl. Phys. Lett. 92, 061102 (2008).
[28] W. M. Gibbons, P. J. Shannon, S. T. Sun, and B. J. Swetlin, Nature 351, 49 (1991).
[29] M. Schadt, K. Schmitt, V. Kozenkov, and V. G. Chigrinov, Jpn. J. Appl. Phys., Part 1 31, 2155 (1992).
[30] E. Ouskova, Yu. Reznikov, S. V. Shiyanovskii, L. Su, J. L. West, O. V. Kuksenok, O. Francescangeli, and F. Simoni, Phys. Rev. E 63, 021701 (2001).
[31] L. Lucchetti, M. Gentili, and F. Simoni, Opt. Express 14, 2236 (2006).
[32] Andy Y. G. Fuh, C. C. Liao, K. C. Hsu, C. L. Lu, and T. S. Mo, J. Nonlinear Opt. Phys. Mater. 11, 57 (2002).
[33] Andy Y. G. Fuh, C. C. Liao, K. C. Hsu, and C. L. Lu, Opt. Lett. 28, 1179 (2003).
[34] M. C. Mauguin, Bull. Soc. Fr. Mineral 34, 71 (1911).
[35] F. A. Jenkins and H. E. White, Fundamentals of Optics, 4th ed. (McGraw-Hill, New York, 1976).
[36] E. Siegman and P. M. Fauchet, IEEE J. Quantum Electron. 22, 1384 (1986).
[37] M. Arendt and R. Jurgen, Introduction to Classical and Modern Optics, 2nd ed. (Prentice-Hall, Englewood Cliffs, New Jersey, 1984).
[38] B. Saad, T.V. Galstyan, M.M. Denariez-Roberge, and M. Dumont, Opt. Commun. 151, 235 (1998).
[39] A. Petrossian and S. Residori, Opt. Commun. 228, 145 (2003).
[40] Andy Y. G. Fuh, C. Y. Lu, T. S. Mo, and M. S. Tsai, Jpn. J. Appl. Phys. 42, 7344 (2003).
[41] A. Murauski, V. Chigrinov, and H. S. Kwok, Liq. Cryst. 36, 779 (2009).
[42] Y. Toko and T. Akahane, Mol. Cryst. Liq. Cryst. 368, 469 (2001).
[43] H. Yokoyama and R. Sun, Jpn. J. Appl. Phys. 39, L45 (2000).
[44] A. Murauski, V. Chigrinov, A. Muravsky, Fion S. Y. Yeung, J. Ho, and H. S. Kwok, Phys. Rev. E 71, 06170 (2005).
[45] K. Y. Lo, C. C. Shiah, and C. Y. Huang, Jpn. J. Appl. Phys. 45, 891 (2006).
[46] L. T. Thieghi, R. Barberi, J. J. Bonvent, E. A. Oliveira, J. A. Giacometti, and D. T. Balogh, Phys. Rev. E 67, 041701 (2003).
[47] I. C. Khoo, S. Slussarenko, B. D. Guenther, M. Y. Shih, P. Chen, and W. V. Wood, Opt. Lett. 23, 253 (1998).
[48] D. Andrienko, V. Reshetnyak, Yu. Reznikov, and T. J. Sluckin, Phys. Rev. E 63, 011701 (2000).
[49] A. Rapini, and M. Papoular, J. Phys. (Paris), Colloq. 30, C4-54 (1969).
[50] X. Nie, R. Lu, H. Xianyu, T. X. Wu, and S. T. Wu, J. Appl. Phys. 101, 103110 (2007).
[51] E. B. Priestley, P. Wojtowicz, P. Sheng, Introduction to Liquid Crystals (Plenium Press, New York, 1975).
[52] I. Jánossy and A. D. Lloyd, Mol. Cryst. Liq. Cryst. 203, 77 (1991).
[53] E. Jakeman and E. P. Raynes, Phys. Lett. 39A, 69 (1972).
[54] R. Yamaguchi, T. Nose, and S. Sato, Jpn. J. Appl. Phys., Part 1 28, 1730 (1989).
[55] Y. H. Wu, Y. H. Lin, H. Ren, X. Nie, J. H. Lee, and S. T. Wu, Opt. Express 13, 4638 (2005).
[56] Y. Y. Tzeng, S. W. Ke, C. L. Ting, Andy Y. G. Fuh, and T. H. Lin, Opt. Express 16, 3768 (2008).
[57] H. Ren and S. T. Wu, Appl. Phys. Lett. 90, 12112 (2007).
[58] D. Fedorenko, E. Ouskova, V. Reshetnyak, and Y. Reznikov, Phys. Rev. E 73, 031701 (2006).
[59] C. Y. Huang, Y. R. Lin, K. Y. Lo, and C. C. Lee, Appl. Phys. Lett. 93, 181114 (2008).
[60] C. Egami, Y. Suzuki, T. Uemori, O. Sugihara, and N. Okamoto, Opt. Lett. 15, 1424 (1997).
[61] C. S. Yelleswarapu, P. Wu, S. R. Kothapalli, D.V. G. L. N. Rao, B. R. Kimball, S. S. S. Sai, R. Gowrishankar, and S. Sivaramakrishnan, Opt. Express. 14, 1451 (2006).
[62] H. C. Yeh, J. D. Wang, K. C. Lo, C. R. Lee, T. S. Mo, and S. Y. Huang, Appl. Phys. Lett. 92, 011121 (2008).
[63] M. Y. Shih, A. Shishido, and I. C. Khoo, Opt. Lett. 26, 1140 (2001).
[64] Andy Y. G. Fuh and T. H. Lin, J. Appl. Phys. 96, 5402 (2004).
[65] F. L. Vladimirov, A. N. Chaika, I. E. Morichev, N. I. Pletneva, A. F.Naumov, and M. Yu. Loktev, J. Opt. Technol. 67, 712 (2000).
[66] M. Kaczmarek, A. Dyadyusha, S. Slussarenko, and I. C. Khoo, J. Appl. Phys 96, 2616 (2004).
[67] S. T. Wu and D. K. Yang, Reflective Liquid Crystal Displays (John Wiley & Sons Press, New York, 1993).
[68] R. Q. Ma and D. K. Yang, Phys. Rev. E 61, 1567 (2000).