摘要

本論文探討建構在奈米液晶聚合物薄膜的二維繞射光柵和布拉格光柵兩種元件的研究與應用。二維液晶聚合物光柵的製作是藉由紫外光聚合過程加入光罩做到光控制相分離反應，結構內部液晶球大小約在200奈米並成週期性排列。二維光柵的繞射光束利用外加電壓或旋轉偏振片方式來開關調控。此二維光柵系統可達成空間光束的系統化調控。
布拉格光柵是利用全像紀錄方式寫入液晶/聚合物混合液內部。此一維光柵包含循環性的液晶與聚合物層,其中液晶球的顆粒尺寸小於200nm。掺雜放射光譜與光柵反射譜邊緣重疊的雷射染料在此樣品內,可觀察到雷射激發現象的產生。

Abstract

The researches and applications of two nano-sized polymer dispersed liquid crystal (PDLC) devices including 2D diffraction gratings and Bragg gratings were investigated in the study. The 2D PDLC gratings are fabricated by light controlled phase separation using a photomask in UV curing. The sizes of LC droplets are ~200nm and formed periodically distributed in the film. The diffracted beams from the 2D PDLC grating were switched by rotating the analyzer and/or applying a voltage. The 2D PDLC gratings can be systematically constructed to support such a beam switching application.
The Bragg gratings are fabricated from LC/pre-polymer mixtures using holographic recording. The 1D grating consists of periodic nano-sized (<200nm) LC droplets and polymer lamellae in the film. Doped with a laser dye whose emission spectrum overlaps the reflection spectrum of the grating, the HPDLC reflection grating can be lased at the band edges of the reflection band gap.

Reference

[1] I. C. Khoo and S. T. Wu, “optics and nonlinear optics of liquid crystals”, World Scientific, Singapore, 1992.
[2] G. W. Gray and J. Goodby, “Smectic Liquid crystals: Textures and structures”, Leonard Hill, 1984.
[3] S. Elston and R. Sambles, “The optics of the thermotropic liquid crystals”, Taylor & Francis, London, 1998.
[4] P. G. de Gennes and J. Prost, “The physics of liquid crystals”, 2nd ed., Clarendon Press, Oxford (1993). Ch6.
[5] R. Repnik, L. Mathelitsch, M. Svetec and S. Kralj, “Physics of defects in nematic liquid crystals”, Euro. J. Phys. 24, 481 (2003).
[6] P. Yeh and C. Gu, “Optics of liquid crystal displays”, Wiley, New York,1999.
[7] P. S. Drzaic, “Liquid crystal dispersions”, World Scientific, Singapore, 1995.
[8] S. Zumer and J. W. Doane, “ Light scattering from a small nematic droplet”, Phy. Rev. A . 34, 3373 (1986)
[9] S. Zumer, “ Light scattering from nematic droplets: anomalous diffraction approach”, Phy. Rev. A 37, 4006 (1989)
[10] J. B. Whitehead, S. Zumer and J. W. Doane, “ Light scattering from a dispersion of aligned nematic droplets”, J. App. Phys, 73, 1057 (1993)
[11] G. P. Crawford, D. W. Allender and J. W. Doane, “Fine molecular anchoring in the escaped-radial nematic configuration: A H-NMR study”, Phy. Rev. A 44, 2570 (1991)
[12] B. G. Wu, J. L. West and J. W. Doane, “Angular discrimination of light transmission through polymer dispersed liquid crystal films”, J. App. Phys, 62, 3925 (1987)
[13] D.R. Cairns, M. Sibulkin and G. P. Crawford, “Switching dynamics of suspended mesogenic polymer microspheres” Appl. Phys. Lett. 78, 2643 (2001).
[14] B. G. Wu, J. H. Erdmann and J. W. Doane, “Response times and voltages for PDLC light shutters”, Liq. Crys., 5, 1453 (1989).
[15] H. Ren and S. T. Wu, “Anisotropic liquid crystal gels for switchable polarizers and displays”, Appl. Phys. Lett. 81, 1432 (2002).
[16] H. Ren, Y. H. Fan, S. Gauza and S. T. Wu, “Tunable-fous flat liquid crystal spherical lens”, Appl. Phys. Lett. 84, 4789 (2004).
[17] H. Ren, Y. H. Fan and S. T. Wu, “Liquid crystal microlens array using patterned polymer network”, Opt. Lett. 29, 1608 (2004).
[18] Y. H. Fan, Y. H. Lin, H. Ren, S. Gauza and S. T. Wu, “Fast-response and scattering-free polymer network liquid crystals for infrared light modulators”, Appl. Phys. Lett. 23, 1233 (2004).
[19] F. Basile, F. Bloisi, L. Vicari and F. Simoni, “Optical phase shift of polymer-dispersed liquid crystals”, Phys. Rev. E. 48, 432 (1993).
[20] H. Ren, Y. H. Lin, Y. H. Fan and S. T. Wu, “Polarization-independent phase modulation using a polymer-dispersed liquid crystal”, Appl. Phys. Lett. 86, 141110 (2005).
[21] H. Kogelnik and C. V. Shank, “Coupled-wave theory of distributed feedback laser”, J. Appl. Phys, 43, 2327 (1972)
[22] H. Kogelnik and C. V. Shank,“Stimulated emission in a periodic structure”, Appl. Phys. Lett. 18, 152 (1971)
[23] H. Kogelnik, “Coupled wave theory for thick hologram gratings”, Bell System Tech. J. 48, 2909 (1969)
[24] M. Nakamura, K. Aiki, J. Umeda and A. Yariv, “cw operation of distributed-feedback GaAs-GaAlAs diode lasers at temperatures up to 300 K”, Appl. Phys. Lett. 27, 403 (1975)
[25] Z. Y. Li and K. M. Ho, “Application of structural symmetries in the plane-wave-based transfer-matrix method for three-dimensional photonic crystal waveguides”, Phys. Rev. B. 68, 245117 (2003).
[26] Z. Y. Li and L. L. Lin, “Photonic band structures solved by a plane-wave based transfer-matrix method”, Phys. Rev. E. 67, 046607 (2003).
[27] M. C. Hutley, “ Diffraction gratings”, Academic Press, London, 1982 p.23
[28] G. Gu, J. R. Lien, F. Dai and J. Hong, “Diffraction properties of volume holographic diffuser”, J. Opt. Soc. Am 13, 1704 (1996).
[29] S. Noda, K. Tomoda and A. Chutinan, “Full three-dimensional photonic bandgap crystals at near-infrared wavelengths “, Science 289, 604 (2000).
[30] J. P. Singh, D. –L. Liu, D. –X. Ye, R. C. Picu, T. –M. Lu, and G. –C Wang, “Metal-coated Si springs: Nanoelectromechanical actuators “, Appl. Phys. Lett. 84, 3657 (2004).
[31] Kazuaki Oya, Tatsuhiro Nakazawa, Shigeo Kittaka and Keiji Tsunetomo, “Ultra-small demultiplexer by use of one-dimensional photonic crystal”, Opt. Lett. 30, 192 (2005).
[32] S. G. Johnson and J. D. Joannopoulos, ” Three-dimensionally periodic dielectric layered structure with omnidirectional photonic band gap”, Appl. Phys. Lett. 77, 3490 (2000).
[33] S. Noda and T. Baba, “Roadmap on photonic crystals”, Kluwer Academic Publishers (2003).
[34] P. N. Prasad, “Nanophotonics”, John Wiley & Sons (2004). Ch9.
[35] Y. Liu, X. Hu, D. Zhang, B. Cheng, D. Zhang and Q. Meng, “Subpicosecond optical switching in polystyrene opal” Appl. Phys. Lett. 86, 151102 (2005).
[36] M. J. Escuti, J. Qi, and G. P. Crawford, “Two-dimensional tunable photonic crystal formed in a liquid-crystal/polymer composite: Threshold behavior and morphology”, Appl. Phys. Lett. 83, 1331 (2003).
[37] S. P. Gorkhali, J. Qi and G. P. Crawford, “Electrically switchable mesoscale Penrose quasicrystal structure”, Appl. Phys. Lett. 86, 011110 (2005).
[38] K. J. Saunders, “Organic polymer chemistry”, Chapman and Hall, London, 1973.
[39] P. Hariharan, “Optical holography”, Cambridge University Press, London, 1984.
[40] H. J. Eichler, P. Gunter and D. W. Pohl, “Laser induced dynamic gratings”, Springer-Verlag, Berlin, 1986.
[41] X. L. Yang, L. Z. Cai, Y. R. Wang and Q. Liu, “Interference technique by three equal-intensity umbrellalike beams with a diffractive beam splitter for fabrication of two-dimensional trigonal and square lattices”, Opt. Comm., 218, 325 (2003).
[42] X. L. Yang, L. Z. Cai, Y. R. Wang and Q. Liu, “Interference of umbrellalike beams by a diffractive beam splitter for fabrication of two-dimensional trigonal and square lattices”, Opt. Lett., 28, 453 (2003).
[43] L. Z. Cai, X. L. Yang and Y. R. Wang, “ Formation of three-dimensional periodic microstructures by interference of four noncoplanar beams”, J. Opt. Soc. A., 19, 2238 (2002).
[44] L. Z. Cai, X. L. Yang and Y. R. Wang, “ All fourteen Bravais lattices can be formed by interference of four noncoplanar beams”, Opt. Lett., 27, 900 (2002).
[45] C. C. Bowley and G. P. Crawford, “Diffusion kinetics of formation of holographic polymer dispersed liquid crystal display materials”, Appl. Phys. Lett., 76, 2235 (2000).
[46]T. J. Bunning, L. V. Natarajan, V. tondiglia and R. L. Sutherland, ”The morphology and performance of holographic transmission gratings recorded in polymer dispersed liquid crystals”, Polymer, 36, 2699 (1995).
[47] T. J. Bunning, L. V. Natarajan, V. tondiglia and R. L. Sutherland, ” Effect of gel-point conversion on the real-time dynamics of holographic polymer-dispersed liquid crystal formation” , Proc. of SPIE 5213, 123 (2003).
[48] S. T. Wu, T. S. Mo, A. Y. –G. Fuh and S. T. Wu, “Polymer dispersed liquid crystal holographic gratings doped with a high dielectric anisotropy dopant”, Jpn. J. Appl. Phys. 40, 6441 (2001).
[49] K. Kato, T. Hisaki and M. Date, “Alignment controlled holographic polymer dispersed liquid crystal for reflective display devices”, Jpn. J. Appl. Phys. 38, 805 (1999).
[50] K. Kato, T. Hisaki and M. Date, “In-plane operation of alignment controlled holographic polymer dispersed liquid crystal”, Jpn. J. Appl. Phys. 38, 1466, (1999).
[51] M. Jazbinsek, I. D. Olenik and M. Zgonik, “Characterization of holographic polymer dispersed liquid crystal transmission gratings”, J. Appl. Phys, 90, 3831, (2001).
[52] D. E. Lucchetta, A. Manni, R. Karapinar, L. Goobi and F. Simoni, “Nano-size polymer dispersed liquid crystals for phase-only optical modulation”, Mol. Cryst. Liq. Cryst. 375, 397, (2002).
[53] S. Matsumoto, K. Hirabayashi, S. Sakata and T. Hayashi, “Tunable wavelength filter using nano-sized droplets of liquid crystal”, IEEE photon. Technol. Lett 11, 442 (1999).
[54] S. W. Leonard, J. P. Mondia, H. M. van Driel, O. Toader, S. John, K. Busch, A. Birner, U. Gosele and V. Lehmann, “Tunable two-dimensional photonic crystals using liquid-crystal infiltration”, Phys. Rev. B, 61, R2389 (2000).