Study On Phase Inversion Of Large Deflection Angle Liquid Crystal Grating

Liquid crystal is both within a certain temperature range between the liquid and crystal properties of the material, so the arrangement structure of liquid crystal molecules are not as strong as the crystal. Liquid crystal molecules are arranged as soft and easy to deformation characteristics, and its molecular shape generally appears as long bar, which has the characteristics of two kinds of optical anisotropy and dielectric anisotropy. As in the case of electric fields, the characteristics of liquid crystal will change, which will lead to the change of refractive index of liquid crystal. Liquid crystal grating is a kind of optical device which uses the change of liquid crystal refractive index to produce phase difference and deflection characteristics. This unique electro-optic effect of the liquid crystal grating is a basic working mechanism for all the liquid crystal optical device. Optical phased array technology is to change the distribution of the light emitted by the local wavefront phase, resorted to the incident light in a particular direction generated phase with each other constructively interfere, obtained in the desired direction of a bunch of high strength beam. The liquid crystal grating is used as optical phased array to realize the wavefront distribution of the beam and the flexible deflection of the beam.In satellite laser communication, laser radar and communication system, the liquid crystal grating being widely applied, the liquid crystal grating can make the laser beam deflection of the flexible control and brings good prospects for the development of the bottleneck of the development of the communication system. In the control of the quality of laser beam, we need to test and analyze the wavefront distribution of the liquid crystal grating phased array. In the near field, beam will be distorted wavefront is deviated from the ideal wavefront phase fluctuations, which is affecting the beam quality in the far field of the decisive reason. In the diagnosis of laser parameters, RMS value that is the average root mean square deviation of the wave front of the wave front at each point is used to indicate the size of the wavefront aberration. Liquid crystal grating wavefront contour will happen drastic changes, In order to accurately measure the wavefront contour of the liquid crystal grating, we must know the influence of the wavefront distribution error of the liquid crystal grating on the performance of the device or in the grating diffraction field. The phase contour of the liquid crystal grating is two step shape, but it is difficult to get the ideal step shape in practical application, so it will have a great impact on the performance of the liquid crystal grating. To make the performance of laser radar, satellite communication and other communication system is stable, it is necessary to test its near-field wavefront characteristics, phase contour inversion device. In order to test the liquid crystal grating phase contour to ensure the performance of liquid crystal grating, this theory using the+1 order of near field diffraction light field inverse diffraction calculation method, using MATLAB simulation analysis, and research by the interference fringe figure algorithm of inverse phase liquid crystal grating contour.In interference measurement technique, the shearing interferometry is a method of using wavefront itself was formed after the dislocation overlap and wavefront interference so as to detect the optical element, optical system or wavefront deformation, can be used to phase recovery. According to the wavefront dislocation in different forms,it can be divided into radial shearing interference, transverse shear, rotation and inversion of four forms. The two kinds of interference methods, including transverse shearing interferometry and radial shearing interference, have been widely studied and applied. Radial shearing interferometry is an effective interference measurement technique to be measured wavefront by radial shearing interferometer were enlarged and narrowed into different multiples in overlapping regions of the interference fringes and the phase of the wavefront deformation distribution were detected the. With the Fizeau interference, Twyman-green interferometer are compared, the radial shearing interference compared with the latter can test large aperture range, and has high precision and disturbance to the environment, less sensitive to mechanical vibration characteristics.This work, we use Matlab to simulate the interference fringe, to restore to be measured by wavefront reconstruction iterative algorithm of radial shearing wavefront. In addition, it can get iteration reconstruction algorithm according to the characteristics of radial shearing interferogram. We simulate the number of points, the number of iterations, the size of the filter window to simulate, analyze the reconstruction of the phase of the results and reconstruction accuracy.The interference fringe pattern is obtained by radial shearing interference experiment, and the fringe pattern is calculated. We can verify that the larger the carrier frequency is, the zero order spectrum and the first order spectrum of the interference light field on the carrier can be obtained. The measurement accuracy of the experimental system is tested by the calibration of the high precision flat surface. The static phase distribution and the phase distribution of the liquid crystal grating are measured, and the measurement of the phase profile of large deflection angle liquid crystal grating can be realized by the single diffraction level inversion method.