Shinji Onodera

Electric conductivity changes of polypyrrole and polythiophene films with heat-treatment

Abstract The electric conductivities of polypyrrole and polythiophene films have been measured as a function of heat-treatment temperature. From room temperature to 150°C, the conductivity of polypyrrole film remained constant. From 150 to 300°C, the conductivity dropped due to the decomposition of polypyrrole and the loss of dopant ion (ClO4−). Above 300°C, the conductivity increased again. Above 750°C, the conductivity was higher than that of the original film due to the formation of carbonaceous materials. The polythiophene film showed a similar tendency to the polypyrrole film. Chemical and spectroscopic methods such as elemental analysis, FT-IR and ESR were employed to determine the origin of the electric conductivity changes.

Fabrication of fluorocarbon polymer-coated silver hollow-glass waveguides for the infrared by the liquid-phase coating method

Abstract Fluorocarbon polymer-coated silver hollow-glass waveguides have been fabricated based on the method of silver mirror reaction for silver, and the dipping method for the fluorocarbon polymer. The waveguides show low-loss properties for the infrared wavelengths except for the wavelength regions of large absorption of the polymer. Er:YAG laser light has been successfully transmitted through the flexible waveguides with small bending losses.

Lensed-taper launching coupler for small-bore, infrared hollow fibers

A new type of launching coupler for small-bore, hollow fibers, consisting of a lens and a tapered hollow waveguide, is proposed to increase the alignment tolerance between an input laser beam and small bore fibers. First, we designed the structural dimensions of the coupler by using a ray-tracing method. Then, a series of experiments employing tapered hollow waveguides made of Pyrex glass was performed to investigate the effectiveness of the new coupler. It is shown that the coupler has a high efficiency with attenuation of around 0.5 dB, especially when the inside of the taper section is coated with a polymer and silver film. In addition, we also show that the coupler has great tolerance for the transverse displacement of a waveguide axis, which gives a 0.1-dB loss increase for a 300-mum displacement.

New fabrication technique of fluorocarbon polymer-coated hollow waveguides by liquid-phase coating for medical applications

A new method to fabricate dielectric-coated hollow waveguides has been proposed based on all liquid-phase techniques. Long silver tubes with an extremely smooth inner surface have been fabricated by using a new process of silver mirror reaction and loss reduction of short silver waveguides has been made by liquid flow-coating of a fluorocarbon polymer.

Fabrication of a frequency conversion device using a novel direction controlled crystal growth method

We have developed a novel direction controlled crystal growth method which makes it possible to fabricate a phase-matched second harmonic generation (SHG) crystal from molten state. A high efficient nonlinear optical crystal, 2-adamantylamino-5-nitropyridine (AANP) was used as an SHG crystal. Glass cells with specific structure made it possible to control the AANP crystal growth direction to the phase-matched angle at 1.55 μm wavelength. X-ray diffraction measurement confirmed that the crystal was fabricated to the direction that we designed.

Transmission characteristics of polyimide-coated silver hollow glass waveguides for medical applications

Polyimide-polymer coated silver hollow glass-waveguides have been proposed for the first time as infrared light transmitting media for the applications in the fields of medicine and infrared sensors. The waveguides with inner diameter of 0.7 mm and length of 1 m have been fabricated by inner coating of polyimide and silver inside a fused- silica capillary tube. By measurements of the loss spectra of the waveguides, it is shown that polyimide-polymer coated silver hollow glass-waveguides have low-loss characteristics at some infrared wavelength regions. As a dielectric material, the polyimide-polymer has many advantages such as high heat-resistance, nontoxicity, durability, and low refractive index over other dielectrics. Moreover, a fabrication method employing liquid-flow coating leads to a possibility of the mass- production of the waveguides.

Thermo-optically Tunable Wavelength Filter with Permanent Refractive Index Grating into Azo-Polymer Waveguide

Refractive index gratings into an azo-polymer waveguide were fabricated by irreversible photo-induced bleaching (photodecomposition) of the polymer. The waveguide grating was formed by exposure of an interference pattern from two laser beams. Coupling characteristics of the waveguide grating were investigated around the infrared wavelength region. The coupling efficiency of the grating was dependent on the polarization direction of the guiding beam. This phenomenon seems to result from the anisotropic refractive index change due to the photobleaching at the vertical plane of the film. Furthermore, we demonstrated a tunable wavelength filter with the refractive index gratings into the azo-polymer waveguide. This filter has a spatial tunability, i.e., wavelength tuning can be attained due to thermooptic refractive index change of the polymer. In the fabricated wavelength filter, the diffraction pass wavelength is tuned over 19 nm at around the 1.3 µm from 5°C to 65°C.

The hydrogen-stretching absorptions and conformations of tetralin-1-ol, chroman-4-ol, thiochroman-4-ol, and indan-1-ol derivatives

The conformations of 1-alkyl (or phenyl)tetralin-1-ols, 4-alkylchroman-4-ols, 4-alkylthiochroman-4-ols, and some secondary and tertiary indan-1-ols have been examined by measurement of the OH stretching absorptions in carbon tetrachloride. For these alcohols, the conformations can be characterized by the following frequencies; quasiequatorial 3 614–3 628 (free OH) and 3 597–3 610 (OH ⋯π hydrogen bonded); quasi-axial, 3 610–3 620 cm–1(OH ⋯π hydrogen bonded).

Fabrication of refractive index grating into an azo-dye-attached EO polymer film by photobleaching

Highly efficient refractive index gratings, 35 percent or more, were fabricated by photobleaching into an azo polymer film with a large second-order optical nonlinearity. From IR spectroscopy, it was confirmed that 532 nm laser light cause photobleaching of azo polymer film effectively. As the modulation depth of relief structure observed by AFM was less than 30 nm, the effect of relief structure observed by AFM was less than 30 nm, the effect of relief structure on the diffraction efficiency is negligible. From these results, we confirmed that the grating obtained in this experiment was mainly caused by photobleaching. We observed that coupling efficiency of the grating is dependent on polarization direction of guiding beam. This is considered to related to the anisotropic refractive index change due to the photobleaching in vertical plane of film.

Lensed taper coupler for hollow waveguides

A launching coupler for hollow fibers consisting of a convex lens and a tapered hollow-guide piece is proposed. We fabricated the coupler which has a conical-tapered, Pyrex glass tube as the tapered section. The bore size of the taper-guides input end is 3 mm and the output end is 0.7 mm which is the same as the size of coupled hollow fibers. The results of preliminary experiments show that the launching system has a large tolerance for the coupling condition between laser light and hollow fibers.