Showing papers by "Satoshi Kawata published in 2000"

Photofabrication of three-dimensional photonic crystals by multibeam laser interference into a photopolymerizable resin

Abstract: Three-dimensional (3D) photonic crystal structures can be fabricated into photopolymerizable resins by using laser beam interference with high precision. Three laser beams interfere into a glass cell filled with a liquid photopolymerizable resin to form a hexagonal periodic structure. Rods are formed in a hexagonal arrangement after being photopolymerzed according to the 3D periodic light distribution which results from the laser’s interference. Two beams of another laser also interfere to form layers which cross perpendicular to the rod array. After photofabrication, the nonsolidified resin is removed by ethanol. The lattice constant can be selected by tuning the angles of the incident beams and the laser wavelength. We have fabricated a 500 μm×500 μm×150 μm photonic crystal structure, the lattice constant of which is 1 μm and contains 150 lateral layers.

Molecular vibration imaging in the fingerprint region by use of coherent anti-Stokes Raman scattering microscopy with a collinear configuration

Abstract: We have developed a new coherent anti-Stokes Raman scattering (CARS) microscopy system with a collinear configuration for use in the fingerprint region. The system consists of a picosecond laser system and a transmission-type laser scanning microscope without a pinhole in front of the detector. The observable Raman-shift region is 900–1750 cm-1, the spectral resolution is 30 cm-1, and the spatial resolution is smaller than 1 µm in the lateral direction and 3.2 µm in the depth direction, with objectives with a numerical aperture of 0.65. CARS spectra and images of polystyrene beads are demonstrated, and CARS imaging of a viable yeast cell is attempted.

Adaptive aberration correction in a two-photon microscope

Abstract: We demonstrate aberration correction in two-photon microscopy. Specimen-induced aberrations were measured with a modal wavefront sensor, implemented using a ferro-electric liquid crystal spatial light modulator (FLCSLM). Wavefront correction was performed using the same FLCSLM. Axial scanned (xz) images of fluorescently labelled polystyrene beads using an oil immersion lens show restored sectioning ability at a depth of 28 mm in an aqueous specimen.

Three Distinct Types of Ca2+ Waves in Langendorff-Perfused Rat Heart Revealed by Real-Time Confocal Microscopy

Abstract: Although Ca(2+) waves in cardiac myocytes are regarded as arrhythmogenic substrates, their properties in the heart in situ are poorly understood. On the hypothesis that Ca(2+) waves in the heart behave diversely and some of them influence the cardiac function, we analyzed their incidence, propagation velocity, and intercellular propagation at the subepicardial myocardium of fluo 3-loaded rat whole hearts using real-time laser scanning confocal microscopy. We classified Ca(2+) waves into 3 types. In intact regions showing homogeneous Ca(2+) transients under sinus rhythm (2 mmol/L [Ca(2+)](o)), Ca(2+) waves did not occur. Under quiescence, the waves occurred sporadically (3.8 waves. min(-1) x cell(-1)), with a velocity of 84 microm/s, a decline half-time (t(1/2)) of 0.16 seconds, and rare intercellular propagation (propagation ratio <0.06) (sporadic wave). In contrast, in presumably Ca(2+)-overloaded regions showing higher fluorescent intensity (113% versus the intact regions), Ca(2+) waves occurred at 28 waves x min(-1) x cell(-1) under quiescence with a higher velocity (116 microm/s), longer decline time (t(1/2) = 0.41 second), and occasional intercellular propagation (propagation ratio = 0.23) (Ca(2+)-overloaded wave). In regions with much higher fluorescent intensity (124% versus the intact region), Ca(2+) waves occurred with a high incidence (133 waves x min(-1) x cell(-1)) and little intercellular propagation (agonal wave). We conclude that the spatiotemporal properties of Ca(2+) waves in the heart are diverse and modulated by the Ca(2+)-loading state. The sporadic waves would not affect cardiac function, but prevalent Ca(2+)-overloaded and agonal waves may induce contractile failure and arrhythmias.

Novel layered structures constructed from metal(II)–chloranilate monomer compounds

Abstract: The new copper(II) and cobalt(II) assembled compounds {(G)2[M(CA)2(H2O)2]}n (M = Cu2+, Co2+; H2CA = chloranilic acid; G = 4-hydroxypyridinium cation (4-pyOH2+), 3-hydroxypyridinium cation (3-pyOH2+)) have been synthesized and characterized. In every compound two chloranilate dianions and two water molecules are coordinated to the metal ion making dianionic monomers, [M(CA)2(H2O)2]2−. The coordination environment around the metal ion is a distorted octahedron, where two water molecules sit in a trans position to each other. [M(CA)2(H2O)2]2− anions form anionic layer structures (1, 3) and an anionic chain structure (2) by using hydrogen bonding interactions. The cations are introduced between the {[M(CA)2(H2O)2]2−}l layers or chains, which are supported by both the hydrogen bonding interaction and the electrostatic interaction between the organic cations and the complexes. In compounds 1 and 3, the organic cations are stacked on each other to form a segregated columnar structure between the {[M(CA)2(H2O)2]2−}l layers. On the other hand, in compound 2, the cations are included in a cage as a dimer. The cage is constructed by the chlorine atoms of CA2− dianions of the chains and the organic cations are anchored to the chain by the hydrogen bonding interactions.

The Photoorientation Movement of a Diarylethene-Type Chromophore

Abstract: We quantified coupled photoisomerization and photoorientation of a diarylethene-type chromophore in films of poly(methyl methacrylate). We found that the chromophore retains partial memory of its o...

Excitation with a focused, pulsed optical beam in scattering media: diffraction effects.

Abstract: To gain a better understanding of the spatiotemporal problems that are encountered in two-photon excitation fluorescence imaging through highly scattering media, we investigate how diffraction affects the three-dimensional intensity distribution of a focused, pulsed optical beam propagating inside a scattering medium. In practice, the full potential of the two-photon excitation fluorescence imaging is unrealized at long scattering depths, owing to the unwanted temporal and spatial broadening of the femtosecond excitation light pulse that reduces the energy density at the geometric focus while it increases the excitation energy density in the out-of-focus regions. To analyze the excitation intensity distribution, we modify the Monte Carlo-based photon-transport model to a semi-quantum-mechanical representation that combines the wave properties of light with the particle behavior of the propagating photons. In our model the propagating photon is represented by a plane wave with its propagation direction in the scattering medium determined by the Monte Carlo technique. The intensity distribution in the focal region is given by the square of the linear superposition of the various plane waves that arrive at different incident angles and optical path lengths. In the absence of scattering, the propagation model yields the intensity distribution that is predicted by the Huygens-Fresnel principle. We quantify the decrease of the energy density delivered at the geometric focus as a function of the optical depth to the mean-free-path ratio that yields the average number of scattering events that a photon encounters as it propagates toward the focus. Both isotropic and anisotropic scattering media are considered. Three values for the numerical aperture (NA) of the focusing lens are considered: NA = 0.25, 0.5, 0.75.

Optical recording of reversed domains in a Ce-doped SBN:75 crystal for bit-oriented three-dimensional optical memory

Abstract: We developed a bit-oriented three-dimensional recording with a Ce-doped Sr0.75Ba0.25Nb2O6 (SBN:75) crystal. The ferroelectric polarization was reversed by a focused laser beam in a crystal with a temperature of 38 °C to form bit data. The recorded domain was stable at 15 °C. The data were read as the refractive-index change induced by spontaneous polarization through the Pockels effect. We wrote a single datum in SBN:75 crystal with ferroelectric-domain reversal and observed the domain image with a phase-contrast microscope. Numerical calculations to estimate the domain image were also performed. The observed results were in good agreement with the numerical expectations.

Triple hydrogen bond directed crystal engineering of metal assembled complexes: the effect of a bifunctional ligand on supramolecular structure

Abstract: The crystal structures of compounds [Hmel]2[M(tdpd)2(OH2)2]·2H2O (M = Ni2+, Co2+; Hmel+ = melaminium cation; H2tdpd = 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile) are reported; the metal complex supramolecular structures can be rationally designed via hydrogen bonding interactions.

Three-dimensional fabrication and observation of microstructures using two-photon absorption and fluorescence

Abstract: We have presented a method to fabricate and image 3D microstructure by using two-photon absorption and imaging with sub-micron resolution capability. This method is based on two-photon-induced absorption and fluorescence into a photopolymerizable resin which is stained with a fluorescent dye, and is able to produce complex microstructuring such as boxes, gear, tubes and icosahedron.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Iron-chloranilate intercalation compounds: synthesis, crystal structures, and thermal properties

Abstract: Hydrogen bond supported new iron-chloranilate assemblies, {(Hpy)[Fe(CA)2(H2O)2](H2O)}n (py = pyridine, H2CA = chloranilic acid, C6H2O4Cl2) (1), and [(phz)2[Fe(CA)2(H2O)2](H2O)2]n (phz = phenazine, ...

Characterization of Organic Photochromic Materials as 3–D Optical Data Storage Media

Abstract: We present our work on data storage and characterization in photochromic materials, and have succeeded in recording data at a total of 26 overlapping layers. The effect of bit depth and bit size were investigated by varying exposure time of the sample to the laser pulses. Bit size and bit depth were found to increase with exposure time and optimizing their values would increase the density of the possible number of data stored in a photochromic medium.

Real-time Ca ion wave imaging in living rat cardiac muscle cells by a confocal multiphoton microscope with a microlens-pinhole array scanner

Abstract: A real-time confocal multiphoton fluorescence microscope was developed to observe Ca 2+ dynamics in living rat-cardiac muscle cells. The real-time imaging was achieved by multifocus excitation of a specimen with a rotating microlens-array disk. A pinhole-array disk for confocal detection was introduced in the microscope to improve the spatial resolution and the contrast of fluorescence images. Ca 2+ wave and Ca 2+ transient in cultured rat-cardiac cells were successfully observed with the developed microscope.

Dynamical Studies of Optically Induced Orientation Processes in Photochromic Isomers : Experiment and Theory

Abstract: Photo-orientation by photoisomerization is quantified for individualizable photoisomers of diarylethene and spiropyran-type chromophores introduced into poly-methyl-methacrylate films. We have meas...

Photo-orientation movement of photoisomerizable chromophores: quantifying analytical theory and application to spectrally overlapping and distinguishable isomers

Abstract: We introduce the analytical theory of couples photoisomerization and photo-orientation both for individualizable and spectrally overlapping isomers, and we use it to quantify the photo-orientation movement of chromophores in polymers including photoisomerization quantum yields. We study photo-orientation processes in A - B photoisomerizable systems where B is unknown. We contrast systems where the isomers are individualizable and without thermal A implied by B isomerization, namely diarylethene and spiropyran-type chromophores in films of poly-methyl- methacrylate, respectively, and systems of nondistinguishable isomers, namely push-pull azobenzenes attached to polyurethane polymers. When diarylethene and spiropyrans are oriented by polarized excitation, the apparent optical orientation changes sign for the ultra- violet versus the visible photochemical transitions: a feature which is due to perpendicular transition dipoles of the B isomer of these chromophores. Photo-orientation reveals the symmetry nature of photoisomerization transitions. We also report on the observation of near-pure photo-orientation by photoisomerization of azo dye in polymers; an observation which is attributed to both the particular molecular structure of the polymer studied and to appropriate photoisomerization quantum yields as well as as fast trans implied by cis thermal isomerization, and is rationalized by the study of photo-orientation of a series of azo-polyurethanes each with distinct differences in the molecular structure of the unit building blocks.

Crystal Structure and Magnetic Property of Cobalt(II) Assembled Compound, {[Co(CA)(bipym)](H2O)2}n (H2CA = chloranilic acid, bipym = 2,2′-bipyrimidine)

Abstract: Cobalt(II) assembled complex compound, ([Co(CA)(bipym)](H 2 O) 2 } n (H 2 CA = chloranilic acid, bipym = 2.2'-bipyrimidine) (1) has been synthesized and structurally characterized by single-crystal X-ray diffraction. Compound 1 crystalizes in the monoclinic, space group C2/c(#15), with a = 16.652(4) A, b = 11.163(3) A, c = 10.081(3) A, β = 116.12(2), V = 1682.4(7) A 3 , Z = 4. The bipym ligands bridge the cobalt centers in bis-bidentate fashion and make zigzag chains. The chains form layer structures by stacking interaction and hydrogen bonding interaction with the help of interstitial water molecules. The temperature dependence of the magnetic susceptibility of 1 shows intramolecular antiferromagnetic interaction with θ = - 39.7 K.

Three-Dimensionally Photorefractive Bit-Oriented Digital Memory

Abstract: Publisher Summary This chapter discusses the systems and the materials suitable for three-dimensional (3D) digital memory with a number of experimental results with the use of photopolymers for read-only memory, lithium niobate crystals as erasable memory, and photochromic organic materials as rewritable photorefractive memory. The comparison between photorefractive 3D memory with a conventional holographic 3D memory and near-field memory is also discussed in terms of dynamic range, noise, recording density, and accessibility. Compared with magnetic data storage, optical memory is advantageous because of its removability, replicability, durability, lightness, and inexpensive price. To exceed the capacity limitation of the surface-recording method of current optical data storage, 3D is introduced with photorefractive materials. Photorefractive materials are suitable for 3D data storage in conjunction with a nonlinear optical system such as the two-photon absorption process of the material for recording and the confocal laser-scanning system for reading.

Photofabrication of 3D photonic crystal by multibeam laser interference

Abstract: 3D photonic crystal structures can be fabricated into photopolymerizable resins by using laser beams interference with high precision. Three laser beams interfere into a glass cell filled with a liquid photopolymerizable resin to form a hexagonal periodic structure. Rods are formed in hexagonal arrangement after being photopolymerzed according to the 3D periodic light distribution which resulted from the lasers interference. Two beams of another laser interfere also to form layers which cross perpendicularly the rods array. After photo-fabrication, the non-solidified resin is removed by ethanol. The lattice constant can be selected by tuning the angles of the incident beams and the laser wavelength. We have fabricated a 500 m X 500 m X 500 m photonic crystal structure, the lattice constant of which is 1 m, and which contains 150 lateral layers.