Hyunjin Oh

A dual-functional monomer having an epoxy and methacrylate group for holographic recording

Photopolymer films containing a dual functional monomer, 2-(oxiranylmethoxy)ethyl 2-methyl-2-propenoate (OEMP), were explored for holographic recording media. OEMP showed high photosensitivity to visible light in the presence of a sensitizer and photoinitiator by the dual polymerization at the methacrylate and epoxide unit. The content of OEMP in the photopolymer films for holographic recording was critical to high optical quality and diffraction of these photopolymer films. With 40 wt% of OEMP the photopolymer film showed a diffraction efficiency of 90% with high sensitivity up to 3.5 × 10−5 cm2mJ−1. The recording stability was longer than 180 days.

Fluorescent Photopolymer for Holographic Patterning

Photopolymer films were prepared for holographic recording and fabrication of multi-dimensional holographic fluorescent patterns. The photopolymer consists of a methacrylate epoxy monomer, photoinitiator, sensitizer, binder polymer, and polyanthracene (PAnt) as a fluorophore. The high diffraction efficiency of fluorescent photopolymer film was determined through a holographic recording system as 60% for a film of 85 µm in thickness. The optimized photopolymer film was applied to fabricate 2 dimensional patterns by laser interference lithography technique and rotation method. A 2-dimensional pattern was confirmed from a fluorescent microscope, which showed crossed pattern having a line width of 0.7 μm.

Diffusion model of monomers in a photopolymer film for holographic recording

Diffusion model of monomers in holographic recording media was investigated to determine diffraction efficiency and the effect of the binder structure on holographic recording in an organic-inorganic hybrid photopolymers. Experimental value and rise of diffraction efficiency for the photopolymer films containing different organic sol-gel precursor (TSPEG) were compared with theoretical plot of diffraction intensity growth against recording time based on the first Harmonic diffusion model, using various material parameters, including the monomer diffusion constant, D, polymerization rate, refractive index of monomer, binder, and polymer. The initial rate of polymerizations in the photopolymer films, evaluated by FT-IR method was compared to the polymerization rate obtained from the simulation. Diffusion time of the photopolymer determined from the simulation was a function of TSPEG content, proving that the side chain in the organic hybrid media affect the diffusion of monomer from the dark area of the photopolymer (non-local polymerization).

Characterization of methacrylate photopolymer films for holography storage

Photopolymer films containing difunctional methacrylate monomer synthesized from s-triazine were prepared for holographic recording. The holographic recording properties of the films were investigated by changing content of the monomers. The optimized composition showed high diffraction efficiency and low shrinkage. Angular selectivity and grating formation from the film will be discussed.

Photopolymers containing triazine monomers with photochromophores for holographic recording

A new photopolymer composite containing triazine monomer and photochromophore was explored as a holographic recording media that show color change after holographic recording. Photopolymer films prepared by mixing s-triazine (ST) methacrylic monomer, photochromic dye, aromatic acrylic monomer, binder polymer, and photo initiator were sensitive to a visible light and polymerized upon excitation with a visible laser light. The real-time diffraction efficiency was determined and correlated to the polymerization of the film. The diffraction efficiency in the presence of photochromophores was similar to that without them. After holographic recording to generate 3D image, an external light source was introduced to change the color of the recorded area. The color change from the 3D image was visible and reversible.