Electro-optical Modulation Properties of Holographic Polymer Dispersed Liquid Crystal Gratings

Holographic Polymer Dispersed Liquid Crystal (H-PDLC) gratings can convert incident light from diffraction to transmission under an applied driving electric field. Therefore, it is expected to be used as a new type of volume holographic diffraction grating to electrically control the output of images matching the ambient light intensity. In H-PDLC gratings, liquid crystal microdroplets dispersed in the polymer matrix are difficult to change their orientation under the anchoring energy of the substrate and polymer matrix, which leads to a high driving voltage. The effect of refractive index modulation and liquid crystal director on the diffraction efficiency were simulated and investigated in this paper. In addition, the optimized H-PDLC grating diffraction efficiency of 97.2% was obtained by adding the nonionic surfactant SPAN80. When the concentration of SPAN80 was 6%, the threshold field intensity compared to the un-doped surfactant grating, decreased from 15 V/mu m to 1.37 V/mu m.