Electronically Controlled Parallel Arrangement Of The Diffraction Properties Of The Liquid Crystal Grating

Since the liquid crystal material was applied in the display apparatus, liquid crystalgrating apparatus gained a lot of attention. Nematic liquid crystal is uniaxial in opticsand dielectric is anisotropic in electricity. And the dielectric of liquid crystal molecule inliquid crystal grating that is made of nematic liquid crystal is changed when the electricfield works on. Then this made it possible to control optical performance with electricfield. When incident light pass the nematic liquid crystal grating with space cycleelectric field, diffractive intensity is controlled by voltage of electric field. So liquidcrystal grating is used in extensive field such as diffraction optics, photoelectric switch,deflexion controlling of light beam.Field-controllable liquid crystal grating is made of two glass-substrates which isimmited nematic liquid crystal. Transparent stripe electrode is shaped on aglass-substrate, and continuum electrode is shaped on another glass-substrate. Theliquid crystal molecule is realigned with space cycle electric field. When incident lightpass liquid crystal grating, the optical path of light changes periodically, and it isfield-controllable liquid crystal grating.The theory of field-controllable liquid crystal grating was analyzed in this paper.Difference iterative method was used to estimate numerically director distributions,equivalent refractive index, and phase delay in both parallel alignment cell and twistedalignment cell, then compared the parallel alignment with twisted alignment. On thebasis of the theory of regular grating, built theoretic model between the liquid crystaland the equivalent regular grating, and computed theoretic data of the zero orderdiffractive efficiency and groove depth. Many parallel aligmnent-liquid crystal gratingswere made and experimented with these. Then compared the experimental data with thetheoretic model, correct coefficient and correct formula of groove depth were gained.Through these formulas, the figures of groove depth and variation of duty cycle wereplotted. Finally, analyzed the properties of the liquid crystal grating with the marginaleffect of electric field.When duty cycle equal to 0.5 of liquid crystal grating, theexperimental data at right angle of incidence was measured, and the even orderdiffraction showed up was found. Because of the influence of the marginal effect of electric field, analyzed the diffractive efficiency,phase delay,variation of duty cycleand groove depth of the liquid crystal grating in the influence of the marginal effect ofelectric field. The analysis on the marginal effect of electric field is the academicfoundation for field-controllable liquid crystal grating.There are two innovations in this paper:(1) Field-controllable liquid crystal grating of parallel alignment was compared withfield-controllable liquid crystal grating of twisted alignment, and the advantageof the parallel alignment cell is showed.(2) On the basis of the theory of regular grating, theoretic model was built betweenthe liquid crystal and the equivalent regular grating, and the properties of theliquid crystal grating with the marginal effect of electric field was analyzed.