Highly sensitive updatable green hologram recording polymer with photoisomerizable azobenzene with highly birefringent acetylene as the side chain

To develop highly sensitive updatable hologram materials, an azobenzene monomer was synthesized herein that supports effective photoisomerization under visible green beam irradiation. Furthermore, an acetylene group was introduced via Sonogashira coupling for higher birefringence. Polymerization was performed on the synthesized azobenzene monomer and on the methyl methacrylate (MMA) monomer, which serves as the skeleton of the film. The structures of all molecules were characterized by nuclear magnetic resonance (NMR) spectroscopy, and UV-Visible absorption spectroscopy was performed to analyze their optical properties. The holographic writing and rewriting capabilities of the newly synthesized azobenzene side-chain polymer were characterized by using a green laser as a writing beam, which showed that a high diffraction efficiency was reliably achievable under low-energy laser irradiation when evaluated with a four-wave-mixing optical scheme.