High-Performance Transmission Holographic Gratings via Different Polymerization Rates of Dipentaerythritol Acrylates and Siloxane-Containing Epoxides

Abstract

Well-defined transmission holographic gratings with high diffraction efficiency were fabricated by irradiating a mixture of photopolymerizable materials with different reaction rates consisting of penta-/ hexafunctional acrylates and siloxane-containing glycidyl ether (88%) or cyclohexene oxide (85%) as radically and cationically polymerizable monomers, respectively, with Nd:YAG laser (λ ) 532 nm). The ratio between the acrylate and epoxide was important to obtain gratings with high diffraction efficiency. They had smooth surface morphologies of well-regulated spacing (0.9 µm). Performance of holographic gratings was optimized by varying the chemical structures of epoxide under various experimental conditions. Introduction of siloxane component into epoxide induced easy diffusion and distinct separation of the epoxide from the polymerized matrix formed by the acrylate, by their low viscosity and incompatible property during the fabrication of the gratings. These gratings were actually used to store a real image.

Dynamic Bragg Angle Shift in the Course of Volume Hologram Formation

“…[8] Epoxides are used as cationically polymerizable monomer to obtain high performance in terms of inducible refractive index contrast, [4] energetic sensitivity [19] as well as mechanical stability. [20] With the aim of optimization, we consider possibilities to further reduce undesired volumetric deformations. To achieve this, a deeper understanding of the basic principles involved in volume changes is required.…”

Preparation of Holographic Gratings of Liquid Crystals Dispersed in Polyurethane Acrylates under Controlled Reaction Conditions

“…[6] Grating Fabrication: Holographic gratings were fabricated by preferential formation of photoproducts in the region of constructive interference arising from the overlap of object and reference laser beams. [20,21] The cell was constructed by sandwiching the prepolymer mixtures between two ITO-coated glass plates with gaps of 4.2-11 mm, adjusted by bead spacers. The prepolymer mixtures were irradiated with an Ar-ion laser (514 nm) at 90 mW cm À2 with exposure times of 8 min.…”

Transmission Holographic Gratings Using Siloxane-containing Liquid Crystalline Compounds. Importance of Chemical Structure of Polymer Matrix Components

“…We reported the influence of siloxane bonds on the viscosity of the compounds, and indicated the importance of low viscosity of siloxane-containing compound in fabrication of gratings with high diffraction efficiency. 28 SEM morphology of the grating was shown in Figure 6. In SEM picture of the ethanol-washed sample in Figure 6, it was observed that the siloxane-containing 11OS3CB well phase-separated from the polymer matrix.…”