Preparation And Study Of Tow-dimensional Polyme/liquid Crystal Holographic Grating

Holographic polymer dispersed liquid crystals (HPDLCs) gratings as a novel optical components,have a very wide range of applications in the measurement, radio astronomy, integrated optics, optical communication, information processing and many other areas.The traditional grating is one-dimensional structure and prepared by beam exposure in two-beam interference field to make the photosensitive monomer polymerization in the horizontal directionz and form the equal-distance and equal-interval stripe parallel to each other.and only records one grating. A two-dimensional grating researched in this article can be simultaneously recorded two gratings in the samples, is equivalent to simultaneously recorded a orthogonal structure of the two one-dimensional grating in the sample. The method to prepare two-dimensional grating is mixed photosensitive monomer into the liquid crystal material and then injected into the sample cell. Put it into two-beam interference field and make it exposure.after 15s rotate 90 degrees and make it exposure another until the photosensitive monomer polymerization completely in the horizontal and the vertical direction of the sample. The diffraction pattern formed by two-dimensional grating is the space lattice when the incident light go through the cell, Besides the application of the above.it can be used for the beam splitter of optical interconnection, modulators and coupling devices, broaden the scope of application.Although the application of two-dimensional holographic polymer dispersed liquid crystal grating is comprehensive, but the preparation method is not mature, there are still many problems at present. Mainly the phase separation is not complete in the polymerization, low diffraction efficiency,and the drive voltage is too high, poor device stability.The liquid crystal and chemical materials used in the system are selected and studyed first in this experimental.and then analyzed the chemical rearrangement process of polymerization photoinitiators.and study the phase separation mechanism of polymer and liquid crystal. Secondly.study the role and impact of each component by changing the irradiation time, light intensity and other parameters in the photopolymerization, in order to increase the degree of photopolymerization and obtain the two-dimensional diffraction polymer/liquid crystal grating with clear separation structure and higher efficiency. Thirdly, based on the analysis to the factors influenced diffraction efficiency, chose different additives to improve the efficiency of light reaction and improve the degree of phase separation. In this paper fluorinated monomers and plasticizer DOP are to selected to improve the grating morphology and the diffraction efficiency, and reduce the driving voltage.Finally, we design and improve the optical path to prepare the two-dimensional polymer/liquid crystal grating with good separation interface, high diffraction efficiency and low driving voltage by two exposure method. At last,we improve the optical path to prepare a two-dimensional polymer /liquid crystal grating with small period.