We experimentally demonstrated a retarder with a wide field-of-view as well as a negative dispersion (ND) of birefringence. We stacked reactive mesogen, which has a positive birefringence, and polymethylmethacrylate, which has a negative birefringence. The out-of-plane retardation (Rth) of the stacked film was 6 nm. This value is about a tenth of that of a general retarder and demonstrates a small change in the retardation (Re) at an oblique viewing angle. The stacked film showed an ND of the birefringence, where Re(450 nm)/Re(550 nm)=0.818 and Re(650 nm)/Re(550 nm)=1.110. The dispersion properties were close to the ideal dispersion of an achromatic retarder and showed a small Re-dependence on the wavelength of light.
We studied the dependence of the electrooptical properties of polymer-dispersed vertical aligned liquid crystals on the surface affinity of the liquid crystal and monomer. The liquid crystal mixture with a smaller contact angle formed more cylindrical droplet and showed uniform vertical orientation of liquid crystal molecules. On the other hand, the liquid crystal mixture with a greater contact angle formed spherical droplet and liquid crystal orientation was deformed near the polymer boundary, resulting in a light leakage between crossed polarizers.
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).
The interaction between electrons and photons satisfying a resonant condition in the boundary between metallic material
and dielectric material can generate a surface-bound wave exponentially decaying away from the interface. Particularly,
the intensity caused by the surface plasmon wave is considerably high on the interface when the incident angle of the
monochromatic wave satisfies the resonant condition. Thus, adopting this wave makes it possible to generate a highly
intense reference wave propagating along the interface in hologram. Recently, it is shown that applications and
researches based on surface plasmon resonance can be applied for photonic integrated circuits and devices. However,
feasible methods to fabricate a nano-scale structure using the surface confined (2-dimensional) wave caused by surface
plasmon resonance require us to use thin photosensitive recording material. Some notable methods to fabricate nanoscale
devices made from PMMA (polymethyl methacrylate) have been already shown. In this paper, by using the
property that the incident monochromatic light can be absorbed in the interface of the metallic medium and the dielectric
medium when a certain resonance condition is satisfied, we propose a wavelength selection filter fabricated by a phase
mask with the pitch of 1061.1nm and phase conjugation holography. In the experiment, two monochromatic light
sources, He-Ne laser with the wavelength of 633nm and second harmonic Nd-YAG laser with the wavelength of 532nm,
will be used. The fabricated lamella metal-coated grating using the phase mask will be shown, and the volumetric metalcoated
photopolymer grating will be used to verify our proposed wavelength selection filter.
Photopolymer films containing s-triazine (ST) methacrylic monomers were explored for holographic recording. Photofunctional s-triazine derivative having polymerizable group was synthesized starting from the reaction of a ST di-thiol derivative with methacryloyl chloride to give ST methacrylic monomer substituted with methylthio group (TRSM). ST methacrylic monomer substituted with ethylene oxy unit (TREGM) was synthesized from the reaction of a diamine substituted ST dichloride derivative with hydroxyl-ethyleneoxy methacarylate (HEMA). Photopolymer films prepared by mixing the s-triazine monomer with binder, additives, and photoinitiator were sensitive to a visible light and polymerized upon excitation with a visible laser. The optimization of holographic recording media was achieved by controlling the concentration and chemical structure of monomer composition in photopolymer films to control the diffusion and polymerization of monomer. The new photopolymer films containing ST methacrylic monomer substituted with ethylene oxy unit (TREGM) showed diffraction efficiency reaching ~ 90%. High diffraction efficiency and fast response for the photopolymer prepared from TREGM monomer were ascribed to the effective monomer compatibility with the binder to result in high optical clarity of the film.
The effect of monomer functionality on the diffraction efficiency of the photopolymer containing multi- and monofunctional monomers was investigated. A mixture of tri-, di-, and mono functional monomers were dispersed in a solution of polysulfone dissolved in organic solvent containing a photo initiator. The monomer contents were varied by changing the ratio between them. The average functionality (Fav = Σ φiFi) was determined, where φi is the mol fraction of the monomer with functionality Fi. The holographic recording was performed and diffraction efficiency (η) of each film was determined by using a 532 nm laser. In the photopolymer film having an optimized composition, η was increased within 20 sec and reached a maximum of >90% with an exposure power of 5 mW laser. The rise of η (response time), maximum η, and stability of η value over prolonged recording were dependent on the monomer structure and composition and the average functionality. The result could be ascribed to the reactivity and functionality of monomers under interference light, to generate refractive index contrast.
Tir- and mono functional monomers were dispersed in a solution of polysulfone in organic solvent containing a photo initiator and other additives. New photopolymer film was prepared by dispersing acrylic monomer in a polysulfone matrix. The Polysulfone was adopted as a binder since it affords transparent thick films with low dimensional changes during holographic recording. Optical property of the photopolymer showed high diffraction efficiency (>90%) under an optimized optical condition at 532nm laser. The angular selectivity for angular multiplexing page oriented holographic memories (POHMs), the maximum diffraction efficiency of the material during holographic recording, the diffraction efficiency of the films as a function of an incident angle of two beams, exposure energy for saturation of the holographic material and application for holographic data storage will be discussed.
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