Naoaki Suzuki

Holographic recording in TiO2 nanoparticle-dispersed methacrylate photopolymer films

We demonstrate permanent holographic storage in the green with high diffraction efficiency and recording sensitivity in TiO2 nanoparticle-dispersed methacrylate photopolymer films. It is shown that the diffraction efficiency as well as the recording sensitivity significantly increase with an increase of nanoparticle concentration. It is also found that volumetric shrinkage during holographic exposure is noticeably suppressed by inclusion of the nanoparticles.

Holographic manipulation of nanoparticle distribution morphology in nanoparticle-dispersed photopolymers

We report on experimental verification of mass transfer of nanoparticles during holographic recording in nanoparticle-dispersed photopolymers. Through direct observations of the microscopic structure of recorded holograms as well as optical measurements of the phase shift between the light interference pattern and a recorded hologram we find that holographic exposure causes nanoparticles to be redistributed from bright to dark regions, leading to periodic assembly of nanoparticles and thereby to formation of high-contrast holograms.

Highly transparent ZrO 2 nanoparticle-dispersed acrylate photopolymers for volume holographic recording

We demonstrate and characterize volume holographic recording in ZrO(2) nanoparticle-dispersed acrylate photopolymer films that have very low scattering loss. More than thirty-fold reduction in the scattering coefficient, as compared with those of previously reported TiO(2) nanoparticle-dispersed photopolymers, is achieved. It is shown that the refractive index modulation as high as 5.3x10(-3), together with substantive photopolymerization-shrinkage suppression, is obtained at the nanoparticle concentration of 15 vol.%. Dependences of nanoparticle concentration and grating spacing on the refractive index modulation are also investigated.

Silica-nanoparticle-dispersed methacrylate photopolymers with net diffraction efficiency near 100%

We demonstrate volume holographic recording in silica-nanoparticle-dispersed methacrylate photopolymers with reduced scattering loss as low as 2%. This is made possible by use of 13-nm silica nanoparticles. As a result a net diffraction efficiency near 100% is achieved for a transmission volume hologram of 45-microm thickness. Grating buildup dynamics are measured for various nanoparticle concentrations, and the effects of nanoparticle size on refractive-index modulation and polymerization shrinkage are also evaluated.

Two-dimensional imaging of atomic distribution morphology created by holographically induced mass transfer of monomer molecules and nanoparticles in a silica-nanoparticle-dispersed photopolymer film

We report an electron-probe microanalysis of a hologram recorded in a silica-nanoparticle-dispersed photopolymer film. We used S and Si atoms as label elements to identify formed polymer and nanoparticle species, respectively. It is found that the periodic density distributions of S and Si atoms are out of phase with each other, indicating that those of the formed polymer and nanoparticles are out of phase each other. This result shows decisive evidence of the mutual diffusion of monomer molecules and silica nanoparticles in the film under holographic two-beam interference exposure.

Real-time phase-shift measurement during formation of a volume holographic grating in nanoparticle-dispersed photopolymers

We describe the real-time measurement of the phase shift between the light interference pattern and a volume holographic grating recorded in dry photopolymers. The time evolution of the refractive index modulation including its magnitude and phase shift is measured for one-component and nanoparticle-dispersed photopolymers. It is confirmed that phase shifts in nanoparticle-dispersed photopolymers depend on the magnitude of the refractive index of nanoparticles relative to that of polymerized monomers.

Diffraction properties of volume holograms recorded in SiO2 nanoparticle-dispersed methacrylate photopolymer films

We report on holographic recording in the green with high diffraction efficiency and recording sensitivity in SiO2 nanoparticle-dispersed methacrylate photopolymer films. Dynamics of diffraction efficiencies and refractive index changes are measured for several SiO2 nanoparticle concentrations and grating spacings. Overmodulation phenomena in the diffraction efficiency are observed in films with the effective thickness of ~32 µm and high nanoparticle concentrations. It is confirmed that the performance of this material system as holographic recording media is comparable to that of recently reported methacrylate photopolymers doped with TiO2 nanoparticles [N. Suzuki, Y. Tomita and T. Kojima: Appl. Phys. Lett. 81 (2002) 4121].

Holographic scattering in SiO2 nanoparticle-dispersed photopolymer films.

We describe an experimental study of holographic (coherent) scattering due to parasitic noise gratings recorded in SiO2 nanoparticle-dispersed photopolymer films. Dependences of film thickness and nanoparticle concentration on holographic scattering losses are evaluated. It is shown that the geometric feature of the holographic scattering pattern in the two-beam recording setup can be explained by the Ewald sphere construction. It is found that holographic scattering becomes noticeable when a film with nanoparticle concentrations higher than 10 vol.% is thicker than 100 microm. The significance of holographic scattering in the characterization of a volume grating recorded in a thick (>100 microm) nanoparticle-dispersed photopolymer film is also discussed.

Volume holographic recording based on mass transport of nanoparticles doped in methacrylate photopolymers

We describe a new type of nanocomposite photopolymer system in which nanoparticles having a large refractive-index difference from formed polymers are dispersed in monomers for permanent volume holographic recording. A model for the holographic grating formation based on the mutual diffusion of monomers and nanoparticles is discussed. The diffraction properties of volume holograms recorded in the nanocomposite photopolymer system are described. Experimental evidence of holographic control of nanoparticle-distribution morphology in a photopolymer is also shown.

Holographic assembly of nanoparticles in polymers for 3D recording and patterning

Holographic manipulation of nanoparticle assembly in polymer and its applications to holographic 3D recording and patterning are described. A statistical thermodynamic model is used to study the kinetics of multidimensional nanoparticle assembling in polymer under holographic illumination. Volume holographic storage using peristrophic multiplexing and nanoparticle pattering in silica nanoparticles-polymer composite films are also demonstrated experimentally.