Due to the rapid development of technology, it is undoubtedly that the liquid crystal (LC) technology plays an important role in human life. Lots of LC displays, such as laptops, smart phones, televisions, and others, appear around our daily lives. Besides, people pay much attention to the international issue of the waste of energy, the studies of bistable LC electro-optical devices become more and more important.
The contents of the thesis include two key topics about multi-stable scattering mode LC light modulators. The first topic is the studies of electro-optical characteristics of ionic LC-doped cholesteric LCs. According to the experimental results, the stable states of transparent and scattering states of the reported LC devices can be electrically switched between each other by applying electric fields with different frequencies. Moreover, these two states are stable states after the applied external field is switched off. Considering this topic, the following three parts, including (1) the switching mechanism, (2) the electro-optical properties, and (3) the causes for obtaining bistabilities, will be discussed in detail. In addition to the permanent stabilization after the applied field is turned off, the reported LC light shutter possesses polarization-independent scattering and good viewing angle. Consequently, this study presents a scattering mode LC light shutter with the advantage of electrical switching, permanent stabilization and high contract ratio. It is definitely believed that such a LC device can be applied to fabricating practical applications of LC devices. In the second part, the studies of the fingerprint textures of dual frequency cholesteric LC doped with dichroic dye are reported. According to the experimental results, the reported light shutter can be electrically switchable between absorption, scattering-absorption and transparent types by applying electric fields with different frequencies. Here, the discussions of the following three parts of (1) the switching mechanism, (2) the electro-optical properties and (3) the comparison with White-Taylor cell, will be given. The main mechanisms of the electrically switchable LC light shutters to both scattering and absorption types by applying an electric field with low frequency, and back to absorption type by applying an electric field with high frequency are reported. Moreover, comparing with the well-known White-Taylor cell, such a reported light shutter has some advantages of the lower operating voltage and shorter response time. Hence, it is believed that the LC light shutter can be applied to be the device for switching between augmented reality (AR) and virtual reality (VR) of easy-carry devices.
 B. Bahoadur, Liquid crystals-applications and uses (World Scientific Press, 1990).
 F. Reinizer, “Beitrage zur kenntiniss des cholesterins,” Monatsh. Chem. 9, 421 (1888).
 Lehmam, “On flowing crystals,” Z. Phys. Chem. 4, 462 (1889).
 S. Chandrasekhar, “Recent developments in the physics of liquid crystals,” Contemp. Phys. 29, 527 (1988).
 E. G. Virga, Variational theories for liquid crystals, (Chapman & Hall London, 1994).
 P. J. Collings, and Michael Hird, Introduction to liquid crystals chemistry and physics, (Taylor ＆ Francis Ltd, 1997).
 P. Yeh and C. Gu, Optics of liquid crystal displays, (John Wiley ＆ Sons, Inc., 2006).
 G. R. Fowles, Introduction to modern optics, 2nd ed., (University of Utah, 1975).
 P. G. de Gennes and J. Prost, The physics of liquid crystals, (Oxford University Press, 1993).
 L. M. Blinov and V. G. Chigrinov, Electrooptic effects in liquid crystal materials, (Springer-Verlag Publishing Co., 1994).
 I. C. Khoo and S. T. Wu, Optics and nonlinear optics of liquid crystals, (World Scientific, 1993).
 G. H. Heilmeier, L. A. Zanoni, and L. A. Barton, “Dynamic scattering: A new electrooptic effect in certain classes of nematic liquid crystals,” Proc. IEEE 56, 1162 (1968).
 E. Dubois-Vilette, P. G. de Gennes, and O. Parodi, “Hydrodynamic Instabilities of nematic liquid crystals under AC electric fields,” J. Physique 32, 305 (1971).
 W. Helfrich, “Conduction-induced alignment of nematic liquid crystals：basic model and stability considerations,” J. Chem. Phys. 51, 4092 (1969).
 G. Mie, “Contributions to the optics of turbid media particularly of colloidal metal solutions,” Ann. Phys. 25, 377 (1908).
 G. H. Heilmeier and J. E. Goldmacher, “A new electric field controlled reflective optical storage effect in mixed liquid crystal systems,” Proc. IEEE 57, 34 (1969).
 E. Jakeman and E. P. Raynes, “Electro-optic response times in liquid crystals,” Phys. Lett. 39A, 69 (1972).
 R. B. Meyer, “Effects of electric and magnetic fields on the structure of cholesteric liquid crystals,” Appl. Phys. Lett. 12, 281 (1968).
 林啟湟，膽固醇手紋結構液晶薄膜及其應用之研究 (國立成功大學物理研究所, 2002).
 D. L. White and G. N. Taylor, “New absorptive mode reflective liquid crystal display device,” J. Appl. Phys 45, 91 (1974).
 G. H. Heilmeier and L. A. Zanoni, “Gust-Host interaction in nematic liquid crystal,” Appl. Phus. Lett. 13, 91 (1968).
 J. Yue, X. Jiang, and A. Yu, “Adsorption of the OH Group on SnO2(110) Oxygen Bridges: A Molecular Dynamics and Density Functional Theory Study,” J. Phys. Chem. C 117, 19 (2013).
 李伯逸，利用電控動態手紋結構製作雙穩態散射型液晶光閥之研究(國立中央大學光電科學與工程學系 2016)