A thiol-ene-based HPDLC grating with s-polarization-dominated 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 the p -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 (Δ n ) on recording intensity and liquid crystal (LC) doping concentration is experimentally investigated. The results show that Δ n 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 Δ n 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.