Shigeru Takarada

Coaxial Configuration of the Gating and Signal Light for a Switching Device of a Dye-Dissolved Polymer Film.

New optical switching devices aimed at the post-liquid-crystal market are currently expected to emerge. We have developed an all-optical system in which the signal light was controlled by the gating light using a thin-film device composed of organic nanoparticles dispersed in a polymer film. Coaxial gating and signal laser beams are focused together onto the thin-film device; this configuration is essential in the present work. The signal light of 694 nm wavelength was switched from a higher transmittance state to a lower transmittance state by irradiating 633-nm-wavelength gating light where the signal light was deflected by a thermal lens temporarily formed by the gating light. The all-optical switching device using the thermal lens method in a nanoparticle-dye-dispersed thin film is the first attempt at using a solid-state system instead of a liquid system currently under investigation, and sub-microsecond operation has been attempted with the organic device.

Noncrystalline Condensation of Densely Dissolved Optically Nonlinear Organic Compound in Polymer Matrices

Optical properties and condensed states of the densely dissolved optically nonlinear organic compound in polymer matrices were investigated by means of optical measurements, structural analysis and pressure tuning spectroscopy. In the investigation of the absorption peak wavelength, 2-methyl-4-nitroaniline (MNA) in poly(methyl methacrylate) (PMMA) exhibited characteristics intermediate between the crystal and the MNA dissolved in solvents, i.e., noncrystalline condensation. This result was consistent with those of X-ray diffraction analysis, second- and third-harmonics generation, IR absorption and 13C-NMR spectroscopies. It has also been revealed that such a system provides the most suitable measuring method of the third optical nonlinear constant for a variety of compounds.

Switching mechanism of an optically-gated optical switch using an organic dye

A versatile optically-gated optical switch using an organic-dye is suitable for light-path switching in an optical communication for various wavelengths of a signal-light. An organic dye for absorbing a gating-light combined with a high-boiling solvent for forming a thermal-lens is properly selected choosing a wavelength of both a gating- and a signal-light. The incidence gating-light passed through a short focal-length lens is absorbed around the focal point and form high-temperature region in the high-boiling solvent, which refract a simultaneously incidence signal-light by a thermal-lens effect. Mechanism of forming a thermal-lens and refracting the signal-light is discussed.

Switching mechanism of an all-optical switch using pulsed gating

A versatile optically gated optical switch using an organic dye is suitable for light-path switching in an optical communication device for various wavelengths of the signal light. We have developed two types of all-optical switch, i.e., a coaxial configuration and a different-axis configuration. The coaxial configuration exhibits a faster response (~80 µs) than the different-axis configuration (~3 ms). Here, the response time of the signal light (1310 nm) is analyzed as a function of both the gating power (pulse height) and pulse width of the gating light (980 nm). The heating and propagation processes in a tiny area around the focal point of both the signal light and the gating light are discussed.

Condensed States and Optical Properties of the Densely Dissolved Organic Compounds in Polymer Matrices by Coprecipitation

Abstract Association of 3,3′-Diethyloxadicarbocyanine Iodide (DODCI) molecules has been revealed in polymer matrices [poly(methyl methacrylate), poly(benzyl methacrylate), etc.], comparing it with association states in appropriate solvents ranging from a dilute concentration (∼10−5 mol/1) to a saturated one, and in a crystal grown in methanol. The association state was investigate by means of optical-absorption and emission spectroscopy, emission lifetime analysis, 13C-NMR spectroscopy and small angle X-ray scattering. Properties of DODCI molecules in polymer matrices were controlled by varying side-chain substituents of the polymers, and DODCI contents.