Akihiro Tagaya

Thin liquid-crystal display backlight system with highly scattering optical transmission polymers

We describe an advanced highly scattering optical transmission (HSOT) polymer backlight system that has shown twice the brightness of a conventional transparent system in spite of its having a thinner backlight. The HSOT polymer that contains optimized heterogeneous structures produced homogeneous scattered light with forward directivity and sufficient color uniformity. Although it was thought that polymers for light-guide plates (LGPs) must be transparent to minimize scattering, we have come to the conclusion that the HSOT polymer, which is not an absorping medium but a scattering medium, is a more suitable medium for LGPs.

HIGH-POWER AND HIGH-GAIN ORGANIC DYE-DOPED POLYMER OPTICAL FIBER AMPLIFIERS : NOVEL TECHNIQUES FOR PREPARATION AND SPECTRAL INVESTIGATION

Rhodamine B (RB), Rhodamine 6G (R6G), Oxazine 4 perchlorate (O4PC), and 4-Dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl-4H-pyran)-doped graded-index (GI) polymer optical fiber amplifiers (POFAs) were successfully prepared by novel techniques to prevent degradation of organic dyes and to enhance solubility of the dyes in methyl methacrylate and in poly(methyl methacrylate) (PMMA). High-power (620 W) and high-gain (33-dB, 2070 times) amplification was achieved for RB-doped GI POFAs based on the spectral investigation of dyes in PMMA bulk. It should be noted that amplification in the low-loss region of polymer optical fibers was achieved in the R6G- and O4PC-doped GI POFA.

High-efficiency organic dye-doped polymer optical fiber lasers

A graded-index polymer optical fiber containing rhodamine 6G in poly(methyl methacrylate-co-2-hydroxyethyl methacrylate) has been fabricated. Lasing behavior of the fiber was observed by pumping with a frequency-doubled Q-switched Nd: yttrium–aluminum–garnet laser. A slope efficiency of 43% and a lifetime of 110 000 shots at a repetition rate of 10 Hz have been observed. With a 1.5 mJ pump energy, an output energy of 640 μJ was produced.

Basic performance of an organic dye-doped polymer optical fiber amplifier

A polymer optical fiber amplifier (POFA) of the graded-index (GI) type, with gain in the visible region, was successfully prepared for the first time, to our knowledge, with the interfacial-gel polymerization technique. An input signal of 0.85Wat 591 nm was amplified to 420W(27-dB gain) by injection of 690W of pump power at 532 nm into a GI POFA with a 0.5-m length. The efficiency of conversion of pump energy to signal amplification was more than 60%.

The advanced highly scattering optical transmission polymer backlight for liquid crystal displays

We have demonstrated the advanced highly scattering optical transmission (HSOT) polymer backlight that was designed by the HSOT designing simulation program. This backlight exhibited approximately three times higher luminance and 20% higher efficiency than the conventional flat-type HSOT backlight of 14.1-inch diagonal because of the microscopic prism structures at the bottom of the advanced HSOT light guide plate. The HSOT polymer containing the optimized heterogeneous structures produced homogeneous scattered light with forward directivity and sufficient color uniformity. Optimization of the heterogeneous structure is important in order to utilize the taper effect and the microscopic prism structures.

Theoretical and experimental investigation of rhodamine B-doped polymer optical fiber amplifiers

High-power (620 W) and high-gain (28 dB) amplification was achieved by a rhodamine B (RB)-doped GI polymer-optical fiber amplifier (POFA) with a l-m length. A theoretical analysis of the amplification in the RE-doped GI POFA was carried out using the rate equation for the fast three level system. The calculated gain behaviour reasonably fit the experimental data. The possibility of higher power (more than 620 W) and higher gain (more than 28 dB) amplification covering a wide range in the visible region is shown from the calculation. Absorption and emission cross sections of RE in poly(methyl methacrylate) bulk were determined and used in the calculation. The values of the cross sections (/spl sigma//sub a/ /sub max/=3.4/spl middot/10/sup -20/m/sup 2/,/spl sigma//sub e/ /sub max/=3.4/spl middot/10/sup -20/ m/sup 2/) were approximately 10,000 times larger than those of Er/sup 3+/ in GeO/sub 2/-SiO/sub 2/ glass.

Zero-birefringence polymer by the anisotropic molecule dope method

We propose using the anisotropic molecule dope method for synthesizing a zero-birefringence polymer that showed no orientational birefringence at any orientation degree of polymer chains. In this method a rodlike molecule with polarizability anisotropy was chosen to compensate orientational birefringence. The zero-birefringence polymer was synthesized by doping of 3-wt.% trans-stilbene as an anisotropic molecule into poly(methyl methacrylate). The zero-birefringence at the 590-nm wavelength in the drawn film and the injection-molded plate made from the zero-birefringence polymer was confirmed by the rotating parallel nicols method. Furthermore, high transparency (37.2 dB/km) of the zero-birefringence polymer at the 633-nm wavelength was confirmed by the light-scattering measurement.

Fabrication and properties of polymer optical fibers containing Nd-chelate

Graded-index poly(methyl methacrylate) optical fibers (GI POF) containing a Nd-chelate have been fabricated. The absorption spectrum of the fiber exhibited several strong bands in the visible and infrared regions. We have observed infrared fluorescence (0.90, 1.06, and 1.3 /spl mu/m) of the Nd/sup 3+/ ion of the fiber at room temperature when it was pumped with an Ar/sup +/-pumped dye laser at 580 nm.

Anisotropic Molecule Dopant Method for Synthesizing a Zero-Birefringence Polymer

We have demonstrated the anisotropic molecule dopant method for synthesizing a zero-birefringence polymer that showed no orientational birefringence at any orientation degree of polymer chains. In this method, rod-like molecules such as trans-stilbene having opposite polarizability anisotropy to that of a host polymer were chosen to compensate orientational birefringence. Orientational birefringence of poly(methyl methacrylate) was completely compensated by doping with some types of anisotropic molecules. Compensation of orientational birefringence for drawn films of the zero-birefringence polymers was analyzed by the rotating parallel nicols method, and orientation functions for polymer main chains and the anisotropic molecules were determined by IR dichroism, which showed that both the polymer chains and the anisotropic molecules were oriented almost equivalently in the drawing process resulting in complete compensation at any draw ratio. Furthermore, the high transparency (37.2 dB/km) of the zero-birefringence polymer was confirmed by light scattering measurements.

High gain and high power organic dye-doped polymer optical fiber amplifiers: Absorption and emission cross sections and gain characteristics

Amplification of high signal gain (36 dB, approximately 4000 times) and high output power (1200 W) was achieved in a Rhodamine B (RB)-doped graded-index (GI) polymer optical fiber amplifier (POFA) based on a prediction in which absorption and emission cross section data were used. The absorption and emission cross section spectra of RB, Rhodamine 6G, and 4-Dicyanmethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) in poly(methyl methacrylate) (PMMA) bulk were determined. The cross section data enable us to predict gain characteristics of RB, R6G, and DCM-doped GI POFA. The wide spectral coverage in the visible is achievable with the GI POFAs doped with several selected dyes.