High Refractive Index Monomers for Improving the Holographic Recording Performance of Two-Stage Photopolymers.

Photopolymers hold great promise for the preparation of transparent volume holographic gratings (VHG), which are core optical elements in many application fields. To improve the holographic recording property of a two-stage photopolymer, four new (meth)acrylate monomers (CTA, CTMA, CTBA, CTBMA) with high refractive indices (1.59-1.63) are designed and synthesized in this study. Using them as one writing monomer, a series of photopolymer samples with different formulations and thicknesses are fabricated for holographic recording. Among them, a formulation containing 9 wt % CTMA shows the best performance. Using it as a recording medium, a VHG with high resolution and diffraction efficiency is constructed. Its refractive index modulation reaches 0.046. Moreover, its total transmittance within 400-800 nm achieves 96.62% after photobleaching. The results indicate that the CTMA-based formulation has great application potential in developing high-performance transparent VHG.