Published papers

Organic materials have bees applied to second and third order nonlinear optical thin film wave guide devices. In second-order devices, the basic material was a side-chained disperse red 1 (DR1)-MMA co-polymer system which was used for frequency doubling in the shorter wavelength region. The co-polymer was spin-coated on a Pyrex substrate and poled under a high DC-electric field over the glass transition temperature. Phase matching at double wavelengths, 532 and 406nm were realized by Cherenkov type in-phasing between fundamental and doubled waves avoiding strong absorption. In the third-order device, the basic was vacuum evavporated PDA film which was applied to all optical bistable waveguide devices together with a DFB structure.

A copolymer of MMA and azo-dye-substituted methacrylate is corona-poled. Cerenkov-type second harmonic generation (SHG) of Nd:YAG laser is observed in the poled polymer waveguide even though there is strong absorption of the SHG wavelength. The total SHG conversion efficiency is 1.72×10-3 %, and the next SHG conversion efficiency in the waveguide is 0.12%.

新たに提案した懸濁重合を用いることにより,非常に単分散で特性のそろった屈折率分布型球レンズを作製する方法を示した。

A high-bandwidth Graded-Index (GI) polymer optical fiber (POF) was successfully obtained by our new random interfacial-gel copolymerization technique. The bandwidth of the GI POF is about 1GHz.km which is two hundred times higher than that of the conventional Step-Index (SI) POF. The total attenuation of the light transmission through these GI POFs is 150-200db/km at 625nm wavelength and the tensile strength is 1600 kg/cm2

A low-loss and high-bandwidth GI POF in which the attenuation of transmission was less than 150dB/km at 650nm wavelength and the bandwidth was several hundreds MHz km has been successfully obtained by a copolymerization process utilizing the difference of the monomer reactivities. The control of the refractive index profile and the light scattering of such GI materials are the theoretically and experimentally investigated.

複屈折の値が正負異なるポリマーを与えるモノマーをランダムに共重合することにより、均一性、透明性に優れる非複屈折性光学ポリマー固体を提案し、そのようなポリマーの合成を行ってきた。その原理と光学特性について解説する。

A low-loss GI Plastic optical fiber in which the attenuation of transmission was 130 dB/km at 650 nm wavelength was successfully obtained by a new interfacial-gel copolymerization technique. Novel optical functional polymer and optically active amorphous polymer which act as polarization modulators were synthesized and characterized.

We have continued some works of the application of a GRIN plastic rod for a CL, the index is gradually increasing (a type of LDR, an application for (-) lens) and decreasing (a type of LFR, an application for (+) lens) to periphery of rod from principal optic axis. The report related to the application of GRIN-complexed LDR and LFR for bifocal CL. GRIN-complexed LFR in certain part and LDR in peripheral part was available to the bifocal of simultaneous type, arranging near zone in central part and distance zone in peripheral part. Also, GRIN-complexed LDR in central part and LFR in peripheral part was available to the bifocal CL of translating type, arranging distance zone in central part and near zone in peripheral part.

米国ボルチモアで開かれた国際会議で低損失,屈折率分布型ポリマー光ファイバーの作製法およびその特性について講演した。

The interfacial-gel copolymerization of 3/1, or 4/1 (wt/wt) MMA-VB monomer mixture followed by heat drawing result in GI POFs with attenuation loss of 212 and 134dB/km at 652nm, respectively, and with bandwidth of 170 and 260 MHz km, respectively, in comparison with 6 MHz km of the current SI POF. Now, it has been confirmed experimentally that GI fibers are tremendously superior to SI fibers for data-carrying capacity, while attenuation losses of both fibers are comparable.

米国ベル研究所の概要、組織、研究内容、研究環境等につき、簡潔に紹介しプラスチック光ファイバの研究の現状につき解説した。

GI-POF whose transmission attenuation is 143dB/km at 651nm wavelength was fabricated by heat drawing the corresponding GI Preform rod. This rod is prepared by the interfacial-gel copolymerization technique of MMA and VPAc. The total scattering loss of the GI preform rod is 〜60dB/km at 633nm. The GI profiles of the optical fibers are almost the same as those of the corresponding preforms with cladding sheaths. The index distributions of their core regions are quadratic against the distance from the center axis. The numerical aperture estimated from the index is 〜0.20.

米国ベル研究所の概要、組織、研究内容、研究環境等につき、簡潔に紹介した。

A GRIN plastic optical fiber was prepared by a heat drawing process of the GRIN preform rod obtained by a new interfacial-gel copolymerization technique. The attenuation loss of the GRIN fiber was 179kB/km at 650nm wave-length and its numerical aperture was 0.20-0.25. To attain low loss and highly dense integrated circuits, steric radial-GRIN optical waveguide components such as GRIN branching, star coupler, multi-coupler, and a 2-D GRIN lens array, were monolithically fabricated by this technique. A novel spherical GRIN sphere lens, whose index function is symmetrical about the center of the sphere, with a low spherical aberration, was prepared by a modified suspension polymerization technique. A W-shaped GRIN sphere has been newly proposed to further reduce the spherical aberration, compared with the parabolic GRIN sphere previously proposed.

One simple example of a rapid flow-through analysis (RFA) system based on ion-selective optode detection was demonstrated, and its performance was discussed. The RFA is a flow analytical method based on a reagentless analyte flow injection system combined with an analyte selective monitor/sensor such as an optical chemical sensor (optode) involving mathematical response simulation using a semi-empirical theoretical response equation. The response of RFA with optode detection can basically be expressed by the equation derived from Fick’s law of diffusion and Kubelka–Munk’s law, and two other variable parameters in relation to the experimental response. Mathematically simulated results using the proposed equation indicated that the equation can be useful for the prediction of the flow analytical response. In the present demonstration of RFA, highly selective ionophores based on 16-crown-5 derivatives were used for the ion-sensing component of the optode for sodium ion determination. A sodium ion-selective optode based on C14-DD16C5 and KD-A3 exhibited high selectivity for sodium ion over potassium ion, with a selectivity coefficient (log Ki,jopt) of −2.6. This optode responded to sodium ion in the concentration range from 10−5 to 10−1 M at pH 8.0 by measuring the absorbance change at 510 nm in the sensing phase of the optode. The RFA system equipped with a sodium ion-selective optode offers a reagent-less advanced ion-determination methodology for conventional flow injection analysis.

Recent status of POF for high speed data communication and telecommunication is reviewed. The GI POF was proposed for the first time 20 years ago at Keio University and several methodologies to fabricate GI POF have been currently proposed worldwide. In this paper, both theoretically and experimentally verify that the most transparent GI POF can be obtained by the polymer dopant system. The relation between the refractive index profile and the dispersion characteristics of GI POF was quantitatively clarified. The refractive index profile of the GI POF obtained by the interfacial gel polymerization process was controlled to enable to transmit the order of gigabit per second bit rate. Furthermore, the accurate approximation of the refractive index profile and consideration of mode dependent attenuation enabled precisely predict the dispersion characteristics of the GI POF.

色素添加型と希土類キレート添加型ポリマー光ファイバー増幅器について、作製法から、光増幅特性まで、全般に渡り詳しく解説している。

マルチメディアを支えるフォトニクスポリマーとして、伝送を司る高速G1型POF、表示を司る液晶ディスプレイの高輝度光錯乱ポリマー導光体バックライトの作製方法及びその光学特性について紹介した。

Recent development of efficient polymer optical fiber amplifier and lasers are reviewed. The gains of a highly efficient organic dye-doped graded index polymer optical fiber amplifiers (POFAs) were measured pumped at 532 nm wavelength. Moreover than 20dB of gain was obtained in the Rohdamine B-doped POFA in wide wavelength range from 560nm to 600nm. The maximum gain of the dye-doped POFA for signal at 580nm was measured to be 36dB. High-power polymer optical fiber was also proposed by utilizing the dye-doped polymer optical fiber, and remarkable lasing properties were obtained. With a 2.5mJ pump power, output energy of 0.6mJ was observed for a Rohdamine 6G-doped polymer optical fiber laser. The simple and innovative functions of dye-doped polymer optical fiber were clarified in this paper.

Recent status of the polymer optical fiber (POF) for high speed communication and telecommunication is reviewed. The GI POF was proposed for the first time at Keio University, and several methodologies to fabricate GI POF have been currently proposed. In this paper, we clarify the great advantage of perfluorinated (PF) polymer which can decrease the intrinsic absorption loss compared with poly methyl methacrylate (PMMA), which is the conventional material of POF. Furthermore, it was found that low material dispersion of the PF polymer is another advantage to obtain the high bandwidth GI POF. It was clarifoed for the first time that the power distribution of modes formed by the mode dependent attenuation was the dominant factor of the higher bandwidth of the GI POF than theoretically predicted bandwidth, while the effect of the mode coupling was small.