Published papers

The development of POF leads to the fundamental question about the transmission loss limit of amorphous polymer glasses. The two intrinsic loss factors of amorphous POFs are molecular visible absorption and scattering due to fluctuation. In this paper, we have investigated the lower limit of the inherent light transmission loss of amorphous polymer glass from its molecular structure by using the Morse potential theory for absorption and the fluctuation theory for scattering. The theoretical lower limit of the attenuation of the amorphous perfluoropolymer is 0.3µm, and is comparable with that of silica fiber. Amorphous perfluoropolymer seems to be a most transparent polymer.

光散乱ポリマー導光体の提案からその液晶バックライトへの応用、多重散乱解析、次世代型光散乱ポリマー導光体バックライトまで、詳しく解説している。

We report on the lasing action of the GI POF containing dyes, such as Rhodamine B, Rhodamine 6G, Perylene Orange, and Pyrromethene 567. These dyes have been incorporate into poly (methyl methacrylate-co-2-hydroxyethyl methacrylate). These fibers were transversely pumped at 532 nm with a frequency-doubled Q-switching ND: YAG laser. Slope efficiency of 24% and output of 1, 3 mJ was obtained with a Rhodamine 6G-doped fiber. A Lifetime of 200,000 pluses at 10 Hz was achieved with a Rhodamine B-doped fiber. GI POF containing a Nd-chelate has also been fabricated. The absorption spectrum of the fiber exhibited several strong bands in the visible and infrared region. We have observed infrared fluorescence (0.90, 1.60, and 1.3µm) of the Nd3+ ion of the fiber at room temperature when it was pumped with an Ar+ -pumped dye laser at 580 nm. The Judd-Often theory was applied to the absorption spectrum of Nd+ in polymer to determine the Judd-Ofelt parameters. From the theory, various radiative properties, such as transition probability, branching ratio, and emission cross section for various emission levels, have been determined and reported.

We encapsulated rare earth ions such as europium and neodymium with organic ligands to in corporate them into polymer materials. Their spectroscopic properties in polymer hosts and organic solutions were studied. Infrared emission has been observed from a neodymium-doped perdeuterated core GI POF.

高速GI型POFの低損失性、耐熱性の向上とともに、情報家電機器間ネットワークインターフェースとして注目を集めるようになってきた。GI型POFの特性の現状を紹介するとともに、特にIEEE1394をベースとした伝送方式にGI型POFを導入し、国際標準化規格としようとする情報家電メーカーの動きなどを紹介した。

近年、期待が高まってきている情報家電機器間の高速ネットワーク、並びに高速オフィス、キャンパスＬＡＮなどの通信メディアとして期待が寄せられているＧＩ－ＰＯＦの伝送損失特性、信頼性、伝送帯域特性および、応用展開に関する近年の動向について述べた。

GI-POFの高速ホームネットワーク、LANへの応用展開について実例を用いた簡易に解説した。

1949年のDebyeらによって書かれた論文につき、解説。

It was clarified for the first time that the slight attenuation increment observed in the previous PMMA dopant system GI POF we reported originated in the excess scattering loss induced by the aggregation of absorbed water into toe POF. Although, the PMMA material generally absorbed two weight% of water at maximum, the low attenuation of the conventional SI POF whose core material is PMMA can be maintained at 70℃, 80% relative humidity (RH) atmosphere because the absorption water might be homogeneously dispersed without any aggregation in the core of POF. On the other hand, addition of dopant material having higher refractive index than that of PMMA is required to form the refractive index distribution in the GI POF, which decreases the amount of water absorption into polymer, because the dopant material is more hydrophobic than PMMA. Therefore, in spite of the small amount of absorbed water such as 0.5wt%, the absorbed water molecules can not be uniformly dispersed but must be aggregated to form heterogeneities in the refractive index of the polymer matrix. It was clarified that a dopant materials that is as hydrophilic as PMMA-dopant system GI POF under high temperature and high humidity atmosphere, and such a suitable dopant system GI POF was proposed.

An optimum index profile offering the highest bit rate communication was formed in a PMMA based GI-POF by modifying the polymerization process. The interfacial gel polymerization process we have proposed to fabricate the PMMA-based GI-POF is capable of forming a nearly optimum refractive index profile. However, the theoretically calculated bandwidth from the measured index profile was reduced compared with the GI POF having optimum index profile. In this paper, we report how to obtain a PMMA-based GI POF having exactly the optimum index profile. The bandwidth of this ideal GI POF was experimentally measured and the very high bandwidth of 2.88GHz even for a 150m fiber length was confirmed. The calculated bandwidth agreed well with experimentally measured one. These results indicate that very low modal dispersion can be expected in a GI POF fabricated by the modified interfacial-gel polymerization process.

A new developed GI POF with high-temperature and high-humidity stability was proposed. As it was found that the high numerical aperture and high glass transition temperature (Tg) at the core center of the GI OPF were key issue to achieve both high-temperature and humidity stability, a partially fluorinated polymer material was adopted to obtain both characteristics in the GI POF. The newly developed GI POF had low-loss, high-bandwidth, high-temperature and humidity stability at 70℃, 80% relative humidity (R.H.) and low bending loss.

The absorption spectra of neodymium (Nd), praseodymium (Pr), erbium (Er), and thulium (Tm) ions in perfluorinated (PF) plastic solutions were measured, and the Judd-Ofelt parameters of the Er and Nd ions have been calculated. The radiative properties of the Nd and Er ions in PF plastic solutions were determined from the absorption measurements and the Judd-Ofelt theory. The fluorescence spectrum of Nd^3+ in a PF plastic solution from 900 nm to 1350 nm was measured for the first time, to our knowledge. Furthermore, the PF plastic films containing lanthanide chelates were fabricated by spin coating, and the refractive indices of the films were measured.

ギガビットの情報を各家庭、オフィスまで導入するアイランド構想とそれにより実現される現状のブロードバンド技術とは一線を画するリアルタイムコミュニケーション社会を展望する。

GI-POFの特性の解説、大学、マンション、小学校などの内部にGI-POFを張り巡らし、双方向のギガビット通信等に付き、最新の研究結果および現在実施されている実証実験等の話を交え解説した。

This review describes recent progress of plastic optical fiber lasers and amplifiers with lanthanides. We focus especially on the design and selection of plastic optical fiber and chelate materials.

We have demonstrated that 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 14.1inch 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 structure.

A high efficiency optical coupler has been developed for high speed plastic optical fiber communication. The coupler was designed for a small photo acceptance area photodiode based on the shape of compound parabolic concentrator. The theoretical efficiency of the coupler for graded index plastic optical fiber (GI-POF) was simulated with ray trace simulation, and the coupling loss was calculated less than 0.4 dB. The coupler was batch fabricated in a glass substrate using sand blast technique. The reflection layer of reflectance 90% was formed by Gold/Nickel mirror plating method. The coupler was bonded with a custom designed high speed PIN photodiode. The photocurrent was 20% higher than the current of a ball lens type PIN photodiode. The cut-off frequency was over 1 Gbps at reverse bias of 1.5 V.

近年のPOFを取り巻く技術的同行について述べた。

Absorption spectra of lanthanide ions in perfluorinated (PF) plastic solution were measured, and the radiative properties were determined by the absorption measurements and the Judd-Ofelt theory. Fluorescence spectrum of Nd3+ in PF plastic solution from 900nm-1350nm, pumped at 580 nm, were measured for the first time. Lasting properties of a Rhodamine 6G-doped graded-index plastic optical fiber laser (GI POFL) and rod laser were investigated. All measurements demonstrated the superior performance of the GI POFL. This paper also discusses the lasing properties on the basis of near-field pattern measurements.

We described 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 (LPGs) must be transparent to minimize scattering, we have come to the conclusion that HSOT polymer, which is not an absorbing medium but a scattering medium, is a more suitable medium for LPGs.