Faculty Profiles - SAKAI Osamu

Papers - SAKAI Osamu

Division display61 - 80 of about 104／ All the affair displays >>

Measurement of electron density in a microdischarge-integrated device operated in nitrogen at atmospheric pressure using a millimetre-wave transmission method Reviewed

Yosuke Ito, Osamu Sakai, Kunihide Tachibana

PLASMA SOURCES SCIENCE & TECHNOLOGY 19 ( 2 ) 2010.4

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

We have diagnosed the electron density in nitrogen plasma generated in a device composed of coaxial-hollow microdielectric-barrier discharges using a millimetre-wave transmission method. At atmospheric pressure the generated plasma occupied almost the entire hollow-electrode space, and the electron density was estimated as 10(12)-10(13) cm(-3). This value is in good agreement with theoretical prediction in a simple particle-balance model. We also studied the effect of small admixtures of H(2)O and O(2) into nitrogen discharges at atmospheric pressure. In the case of H(2)O addition, the measured electron density was lower than that in pure nitrogen, in particular at high reduced electric fields, due to the increase in the loss processes of electrons. In the case of O(2) addition, the electron density decreased with an increase in O(2) concentration due to the additional loss process through the formation of negative ions.

DOI： 10.1088/0963-0252/19/2/025006

Web of Science

Study of plasma enhanced chemical vapor deposition of ZnO films by non-thermal plasma jet at atmospheric pressure Reviewed

Yosuke Ito, Osamu Sakai, Kunihide Tachibana

THIN SOLID FILMS 518 ( 13 ) 3513 - 3516 2010.4

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Plasma enhanced chemical vapor deposition using a non-thermal plasma jet was applied to deposition of ZnO films. Using vaporized bis(octane-2,4-dionato)zinc flow crossed by the plasma jet, the deposition rate was as high as several tens of nm/s. From the results of infrared spectra, the films deposited at the substrate temperature T(sub) = 100 degrees C contained a significant amount of carbon residue, while the films prepared at T(sub)=250 degrees C showed less carbon fraction. The experimental results confirmed that the plasma jet decomposed bis(octane-2,4-dionato)zinc in the gaseous phase and on the substrate, and that there should be the critical Tsub to form high-quality ZnO films in the range from 100 to 250 degrees C. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2009.11.034

Web of Science

Microplasma array with metamaterial effects Reviewed

Osamu Sakai, Teruki Naito, Takuya Shimomura, Kunihide Tachibana

THIN SOLID FILMS 518 ( 13 ) 3444 - 3448 2010.4

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Metamaterial effects emerging from a spatially-arranged microplasma array was investigated at microwave frequencies. With elaborated spatial designs of periodic columnar microplasmas, they serve as a converter of microwaves in the complex plane with various functions. Composites of microplasmas and metal wires show extraordinary properties for electromagnetic waves, such as negative-refractive index, which have not been naturally available. These two aspects of microplasma arrangement will open novel features beyond the conventional materials, which can be referred to as plasma metamaterial effects. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2009.11.040

Web of Science

円筒プラズマ列による表面波導波路の動的形成

前田潤, 内藤皓貴, 酒井道

電気学会研究会資料. EMT, 電磁界理論研究会,2010 (1), pp. 179-183 2010.1

円筒プラズマ列による表面波導波路の動的形成 (レーザ・量子エレクトロニクス)

前田潤, 内藤皓貴, 酒井道

電子情報通信学会技術研究報告,109 (403), pp. 179-183 2010.1

円筒プラズマ列による表面波導波路の動的形成 (フォトニックネットワーク)

前田潤, 内藤皓貴, 酒井道

電子情報通信学会技術研究報告,109 (401), pp. 179-183 2010.1

円筒プラズマ列による表面波導波路の動的形成 (光エレクトロニクス)

前田潤, 内藤皓貴, 酒井道

電子情報通信学会技術研究報告,109 (402), pp. 179-183 2010.1

Interaction between Dielectric Barrier Discharge and Positive Streamer in Helium Plasma Jet at Atmospheric Pressure Reviewed

Keiichiro Urabe, Yosuke Ito, Osamu Sakai, Kunihide Tachibana

JAPANESE JOURNAL OF APPLIED PHYSICS 49 ( 10 ) 2010

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN SOC APPLIED PHYSICS

We have investigated the discharge mechanisms in a helium plasma jet with a coaxial dielectric barrier discharge (DBD) configuration, which can generate low-temperature plasma plume mainly by positive corona streamer propagation. In this study, we focused on the relationships between the coaxial DBD inside a glass tube and the positive streamer propagating in the plasma plume, using novel types of electrode configurations composed of insulated electric wires. The discharge characteristics were investigated by measuring plume length, discharge currents of the DBD, and the line-integrated density of helium metastable atoms in the plume. The experimental results indicate that the excited-species density in the plume is largely dependent on surface-charge density accumulated by the DBD. Moreover, we analyzed the spatiotemporal distribution of electrical potential around the tube exit by the finite element method, and discussed the mechanism determining plume length. (C) 2010 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.49.106001

Web of Science

プラズマアレイのメタマテリアル効果を用いた電磁波の動的複素制御

下村卓也, 内藤皓貴, 前田潤, 酒井道, 橘邦英

電気学会研究会資料. EMT, 電磁界理論研究会,2009 (102), pp. 97-102 2009.11

Mode Change Observed on Spatial Distribution of Microplasma Emission in a Microdischarge Cell with a Floating Electrode Reviewed

Dae-Sung Lee, Osamu Sakai, Kunihide Tachibana

JAPANESE JOURNAL OF APPLIED PHYSICS 48 ( 10 ) 2009.10

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN SOCIETY APPLIED PHYSICS

A microplasma device fabricated on a silicon substrate with a floating electrode inside the microdischarge space was investigated-to determine the dependences of discharge properties in neon gas on the gas pressure p and the characteristic-dimension D. With a decrease in p towards the condition of the minimum ignition voltage, the spatial emission distribution in the negative phase of the applied bipolar pulsed voltage changed from a hollow pattern with a bright periphery to a concentrated bright pattern in the central area above the floating electrode, which was similar to that in the positive phase. This observation encourages us to make this device structure to provide a brighter light source at the microscales for various photonic applications. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.106002

Web of Science

Reduction of CO2 solute by hydrogen microplasmas in an electrolyte Reviewed

Osamu Sakai, Tadasuke Morita, Noriaki Sano, Tatsuru Shirafuji, Tomohiro Nozaki, Kunihide Tachibana

JOURNAL OF PHYSICS D-APPLIED PHYSICS 42 ( 20 ) 2009.10

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

CO2 as a solute of aqueous solution was deoxidized by hydrogen microplasmas generated in an electrolyte. Dielectric barrier discharges were generated in H-2 microbubbles created by electrolysis, and optical emission spectra included carbon-oriented lines as well as an atomic H line. From a chromatogram of a gas in a trap on the electrolyte surface, CO was detected, which was a product of the reduction reaction of CO2 induced by underwater hydrogen microplasmas.

DOI： 10.1088/0022-3727/42/20/202004

Web of Science

大気圧プラズマ－基礎と応用 Reviewed

橘邦英, 小田哲治, 堀勝, 渡辺隆行, 高井治, 白藤立, 明石治朗, 赤塚洋, 秋津哲也, 秋山秀典, 内野喜一郎, 大竹尚登, 大参宏昌, 岡崎健, 岡本幸雄, 小田昭紀, 小野亮, 垣内弘章, 河野明廣, 小駒益弘, 児玉英之, 酒井道, 櫻井彪, 佐藤岳彦, 佐藤正之, 佐野泰久, 白井肇, 神野雅文, 高木浩一, 高島成剛, 竹田圭吾, 寺嶋和夫, 栃久保文嘉, 永津雅章, 中野俊樹, 中村圭二, 西脇彰, 野崎智洋, 水野彰, 安武潔, 山内和人, 山村和也, 湯浅基和

大気圧プラズマ－基礎と応用 2009.10

Microplasma-Induced Deformation of an Anomalous Response Spectrum of Electromagnetic Waves Propagating along Periodically Perforated Metal Plates Reviewed

Dae-Sung Lee, Osamu Sakai, Kunihide Tachibana

JAPANESE JOURNAL OF APPLIED PHYSICS 48 ( 6 ) 2009.6

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN SOCIETY APPLIED PHYSICS

Metal plates with two-dimensional hole arrays showed unusual responses of electromagnetic waves, and in this study microplasmas were generated in the holes to deform their properties dynamically and to induce novel frequency-dependent permittivity. Transmitted electromagnetic waves in millimeter wavelength range exhibited attenuation of anomalous transmittance around cutoff frequency of equivalent waveguide when microplasmas were present. On the contrary, the reflected waves were significantly enhanced around such a frequency, where reflectance is at minimum in the case without microplasma generation. These experimental results indicated resonance phenomenon which is usually called spoof surface plasmons, and dynamic change of dielectric constant in the medium inside the holes induced by microplasmas shifts their resonance frequency. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.062004

Web of Science

マイクロプラズマによる電磁波メタマテリアル Reviewed

酒井道, 橘邦英

應用物理,78 (5), pp. 437-441 2009.5

金属の周期的微細構造によるテラヘルツ波の伝搬制御

古川龍, 酒井道, 橘邦英

電気学会研究会資料. EMT, 電磁界理論研究会,2009 (22), pp. 63-66 2009.1

金属の周期的微細構造によるテラヘルツ波の伝搬制御(フォトニックNWシステム・デバイス,フォトニック結晶・ファイバとその応用,光集積回路,光導波路素子,光スイッチング,導波路解析,及び一般)

古川龍, 酒井道, 橘邦英

電子情報通信学会技術研究報告. LQE, レーザ・量子エレクトロニクス,108 (419), pp. 163-166 2009.1

Underwater microdischarge in arranged microbubbles produced by electrolysis in electrolyte solution using fabric-type electrode Reviewed

Osamu Sakai, Masaru Kimura, Tatsuru Shirafuji, Kunihide Tachibana

APPLIED PHYSICS LETTERS 93 ( 23 ) 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

Pulsed microdischarge was generated in microbubbles produced by electrolysis in an electrolyte solution without external gas feed by using a fabric-type electrode. The electrode structure not only allowed low-voltage ignition of the atmospheric-pressure discharge in hydrogen or oxygen containing microbubbles but also worked effectively in producing and holding the bubbles on its surface. The generation of reactive species was verified by optical emissions from the produced microplasmas, and their transport into the solution was monitored by the change in hydrogen concentration.

DOI： 10.1063/1.3006348

Web of Science

Experimental verification of complex dispersion relation in lossy photonic crystals Reviewed

Teruki Naito, Osamu Sakai, Kunihide Tachibana

APPLIED PHYSICS EXPRESS 1 ( 6 ) 2008.6

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN SOC APPLIED PHYSICS

The complex wave number in lossy photonic crystals composed of microplasmas was verified experimentally by measuring the refractive index and the transmittance in a microwave range. These experimental results coincide with the dispersion relation obtained by a modified plan-wave expansion method. In particular, an extraordinary reduction of attenuation was observed in a certain frequency band, which is attributed to a loss term in the dielectric function and periodicity in the structure. These results indicate that a method of dynamic control for electromagnetic waves can be realized using of the dispersion relation in complex space. (C) 2008 The Japan Society of Applied Physics.

DOI： 10.1143/APEX.1.066003

Web of Science

Characteristics of metamaterials composed of microplasma arrays Reviewed

Osamu Sakai, Takui Sakaguchi, Teruki Naito, Dae-Sung Lee, Kunihide Tachibana

PLASMA PHYSICS AND CONTROLLED FUSION 49 ( 12B ) B453 - B463 2007.12

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

Functional arrays of microplasmas were designed for the purpose of controlling electromagnetic waves in the range 10 - 100GHz. A two-dimensional square-lattice array of microplasma columns was proved to have photonic-crystal-like properties showing the presence of photonic band gaps and flat bands. A one-dimensional linear array of cold cathode fluorescent lamps (CCFLs) embedded in between the truncated strip lines showed the resonant transmission characteristics due to the surface-wave modes corresponding to the flat-band frequencies. Another one-dimensional configuration of CCFLs vertically aligned along both sides of a coplanar strip line showed peculiar behavior at the lower and higher edges of the band gap. These unique wave-propagation properties are attributed to the periodic structures of which pitches are comparable to or smaller than the wavelengths of electromagnetic waves. Therefore, these artificial arrays are potential metamaterials, which can be used for plasma devices controlling electromagnetic waves.

DOI： 10.1088/0741-3335/49/12B/S43

Web of Science

Properties of electromagnetic wave propagation emerging in 2-D periodic plasma structures

Osamu Sakai, Kunihide Tachibana

IEEE Transactions on Plasma Science 35 ( 5 I ) 1267 - 1273 2007.10

Publishing type：Research paper (scientific journal)

Periodic structures in plasmas form unique dispersions of electromagnetic waves, which are examined in numerical calculation. Above electron plasma frequency, where waves equivalently propagate in dielectric media, plasma arrays with 2-D periodicity produce frequency regions of forbidden propagation, like band gaps in a photonic crystal. Below electron plasma frequency, where waves are usually forbidden to propagate due to cutoff phenomenon, bulk plasmas with periodic holes can become wave-propagating media in which localized surface modes play an important role. Such features give rise to concepts of dynamic wave controllers that change their inner electron density in time. © 2007 IEEE.

DOI： 10.1109/TPS.2007.906133

Scopus

　 PREV - NEXT 　

<SAKAI Osamu>

Papers - SAKAI Osamu