| Liquid crystal optics is a synthetic and marginal subject. It relates to physics, chemistry, biology, and other based subjects. As a new material, it has been applied more and more widely. As a condensation product, its characters are between the isotropic solid crystal and the anisotropic liquid. It is ordered fluid. As the macroscopical characters are concerned, it have the flowing power and viscidity like liquid, and the anisotropy like crystal.lt has birefringence, Bragg reflection, diffraction and optical rotation like crystal. Furthermore, it has thermal light effect, electrical light effect or magneto optical effect in outside field. Now, liquid crystal technology has been used in many fields widely, as electrical display device, optic communications, optical information processing, the public nuisance of chemical industry, the oriented polymer of macromolecular reaction, the nondestructive evaluation and microwave determination of aviational machine and metallurgic product, checking skin cancer in medicine, body temperature measurement, etc. It has showed the great superiority. In many characters of liquid crystals, the voltage-dependent birefringence is the most important character. When let it in the electric field, the oritation of liquid crystal molecule will change. It induced the optic axis to change. At last, the birefringence will change. This is the Voltage-dependent birefringence of liquid crystal.Itis applied in liquid crystals display, light communication, light information processing, etc. The Voltage-dependent birefringence of liquid crystal is widely used because of many merits. (l)Its applicable spectral range is extraordinarily broad. Many nematic LCs show very large birefringence and good transparency in both near-UV, visible, and IR regions (except in the vicinities of some resonant electronic and molecular vibrational absorption bands). (2)The required voltage is very small. Usually, a large birefringence change (0.2) can be achieved by a relatively small voltage(a few volts, depending on the LC used).Its wavelength taxability is determined by the controlled birefringence of the liquid crystal used. (3)Continuous variable birefringence. The Continuous variable birefringence can be achieved by a relatively small voltage.(4)No deviation in the outgoing beams takes place.(5)Applied voltage can compensate the temperature effect on the filter' s perfermance. (6)The low lost, high recurrence rate, and good stability. (7)The device fabrication is simple and cost is low. So, studying deeply in the LC voltage-dependent birefringence is very necessary. But in china, the study of this character is mostly the application. The special study is short. Furthermore, one shortage, that we don' t often think of the absorption, is prevalent. This paper studied the voltage-depended birefringence of liquid crystal, thinking of the absorption of LC.The theme includes four sections. The function and general situation in present of LC voltage-dependent birefringence was introduced in the first chapter. Because of the wide application, more and more scientists have been interested in studying LC voltage-dependent birefringence. Now, in china, many scientists are studying it, especially abroad. In china, they mainly studied in the application, and they did not think of the absorption of LC molecules.The basic knowledge of LC is introduced in the second chapter, especially the nematic liquid crystal. The nematic liquid crystal molecule is rodlike with big slenderness ratio. The barycenter of molecule is not long-range order. It has fluidity like liquid. The molecules do not tirer up. They can slide up and down, left and right, forward and backward. They only hold parallel or nearly parallel in the long axis orientation of the molecules. The interactivity of the molecules is weak. It belongs to Vander waals attractive force. The biggest character of nematic liquid crystal is that the orientation of the molecules leans to the same direction when LC is affected by magnetic field, electric field,... |
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