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

Holographic Polymer Dispersed Liquid Crystal (HPDLC) 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 $\mathbf{9 7. 2 \%}$ 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 $15 \mathrm{~V} / \mu \mathrm{m}$ to $1.37 \mathrm{~V} / \mu \mathrm{m}$.