Shin-ichi Abe

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.

Transmission and attenuation of the dominant mode in uniformly bent circular hollow waveguides for the infrared: scalar analysis

A numerical evaluation is conducted of electric field distributions, phase constants, and attenuation constants of the lowest eigenmode in the general class of uniformly bent circular hollow waveguides. The analysis is based on a scalar equation, and numerical results are compared with those of existing approximate theories. Normalized forms of attenuation constants are presented for the parallel and perpendicular polarizations to the bending plane by using structural and material parameters. For sharply bent waveguides, useful and simple expressions are derived for the attenuation constants of the TE and TM modes in the corresponding slab geometry with suitable weighting parameters. >

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.

Graphical representation of mode selectivity in hollow waveguides with and without inner dielectric layer: slab waveguide model

Abstract The degree of mode selectivity in hollow waveguides is defined by using the ratios between the attenuation constants of the dominant and higher order modes. The mode selectivity has been evaluated numerically as a function of the complex refractive index of the cladding material. The degree of mode selectivity is generally shown to be less than 2. However, it can be made larger than 2 without sacrificing the low-loss property of the waveguide by means of a dielectric coating.

Transmission and attenuation of vector modes in uniformly bent circular hollow waveguides for the infrared

Electric field distributions and attenuation constants of the eigenmodes in uniformly bent circular hollow waveguides have been evaluated based on a vector wave equation deduced from Maxwells equations. A diagram representation of the parameter describing mode properties is introduced. It is numerically shown that vector modes gradually approach linearly polarized modes when the bending radius becomes small. A relation between attenuation constants in sharply bent circular and slab hollow waveguides is also discussed where the electric fields concentrate near the outer edge of the core. >

MACULAR CHOROIDAL OCCLUSION IN DYSPLASMINOGENEMIA

Abstract: The authors describe a family with dysplasminogenemia. This diagnosis was based on a lowered ratio of functional plasminogen activity to immunologic plasminogen antigen level, associated with fundus abnormalities. The proband is a 31‐year‐old woman with Graves disease who had choroidal occlusive lesions of the macula in both eyes. The results of the laboratory examination indicated that the patient was a homozygote for dysplasminogenemia. Similar examinations of the patients parents and siblings showed their plasminogen levels to be 50% below normal. The thrombotic tendency in this disorder appeared to be responsible for the pathogenesis of the macular choroidal occlusion. RETINA 11:423‐425, 1991

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.

Heat-resisting polymer-coated silver hollow glass waveguides for medical applications

Heat-resisting polyimide-coated silver hollow glass waveguides have been fabricated for infrared medical laser light transmissions. The waveguides have inner diameters of 700 and 530 micrometers and the length of 1 m. The measurements of the guiding loss spectra show the low-loss property of the waveguides at the desired wavelengths. Moreover, Er:YAG laser light has been transmitted by the 700 micrometers -bore waveguide with the losses as low as 2.2 dB even when the waveguide is bent with a bending radius of 15 cm (180 degree(s)-bend).