A thiol-ene-based HPDLC grating with s-polarizationdominated diffraction

Holographic Polymer-Dispersed Liquid Crystal (HPDLC) gratings exhibit excellent electro-optical performances due to their unique optical characteristics and tunability. However, the previously reported HPDLC gratings where thep-polarization response dominates in their diffraction, i.e., the diffraction efficiency of HPDLC gratings in p-polarization is much larger than that in s-polarization. This Letter reports a thiol-ene monomer-based HPDLC grating, which exhibits a high s-polarization diffraction efficiency rather than p-polarization. The dependence of refractive index modulation (Δn) on recording intensity and liquid crystal (LC) doping concentration is experimentally investigated. The results show that Δn is able to reach as high as 1.93 × 10^-2 in s-polarization and 1.21 × 10^-2 in p-polarization with an optimum recording condition. Combining with the morphology examinations, the results imply that the Δn strongly depends on the ratio of LC-rich and polymer-rich phases in the grating. Moreover, we confirm that a lower recording intensity leads to a larger LC droplet size formed by holographic recording and thereby results in a decrease in threshold driving voltage of HPDLC gratings. We believe that the finding of s-polarization-dominated diffraction in the proposed thiol-ene photopolymer provides a new direction for HPDLC grating design.