Fabrication of two-dimensional hexagonal lattice Holographic Polymer-dispersed Liquid Crystal grating with variable periods

摘要

In this paper, we reported a method to fabricate 2D hexagonal lattice Holographic Polymer-dispersed Liquid Crystal (H-PDLC) grating with variable period by using cylindrical waves interfere with plane waves. In order to separate polymer from liquid crystal syrup, a 532nm laser with an exposure intensity of 16mw/cm2 was used to expose. Two steps exposure techniques was adopted in the experiment with the expose time of 2s and 60s in the separate steps to form the 2D gratings. In the second exposure step, the sample was rotated by anti-clockwise 60° to form 2D hexagonal lattice structure within H-PDLC grating. The theoretical equations for describing the variable period grating is analyzed. What's more, the diffraction efficiency and other characteristics of this grating is also studied experimentally. The experimental result shows that fabricated grating with the continuously changing periods varying from 1.679 micrometer to2.051 micrometer within the radius of 6 mm circle sample area, which is corresponded to the theoretical simulation quite well. The first-order diffraction efficiency was tested around18.3%. The intensity of transmission beam increased from 15.6% to 73% when applied with the driving voltage from zero to the maximum of 90 V. This 2D grating has the potential application in diffractive optics such as a tunable multi-wavelength organic laser device etc.