bluuebunny/crossref_metadata_2025 huggingface dataset:
Single-Wavelength 5.6 kW Direct Diode Laser with a High-Efficiency Beam Combination
Authors: Miyajima Hirofumi , Kan Hirofumi , Gao Xin , Uchiyama Takayuki , Hiruma Teruo , Yamanaka Masanobu , Izawa Yasukazu
Published: February 2005

Our group developed a new optical system equipped with a slit mirror to combine the output power from two LD stack modules (30 bars each) and focus them into a single beam. The new device realized a CW output power of more than 3 kW with a transfer efficiency of 92%. Furthermore, by combining beams from two added stack modules to the main optical path using polarization coupling, we have achieved a CW output power of 5.6 kW with a single wavelength of 808 nm. The focused spot size was 2.4 mm×0.5 mm (the power intensity was 467 kW/cm2) at a practical focal length of 100 mm. The transfer efficiency from the LD output to the focal spot was estimated to be 86.5%. The total energy efficiency against the input electricity was approximately 45%. This value is the highest ever reported in a high-power LD applied to material processing, and a full threefold higher than that of the diode-pumped Nd:YAG laser, a device heretofore known to be highly efficient (at around 15%).
Tuning Near-Infrared Optical Properties of Aromatic Model Compounds by Substituents
Authors: Yen Cheng-Tyng , Chang Yung , Chen Wen-Chang
Published: February 2005

In this study, the effects of substituents on the near-infrared (NIR) absorption spectra of model compounds were examined theoretically and experimentally, including benzene (B), fluorobenzene (FB), 1,4-difluorobenzene (DFB), and 1,4-bis(trifluoromethyl) benzene (6FB). It was found that a stronger electron-withdrawing substituent resulted in a smaller C–H bond length and thus a blue-shifted overtone position. Thus, the order of B > FB > DFB > 6FB was found for the positions of C–H fundamentals and overtones. The variations of optical windows were primarily influenced by the C–H molar density as well as by the shifting of the absorption band by the substituent. A pseudo compound (PC) with the same C–H number density as the 6FB but with the same band position as B was used to address the effect of a polarized substituent on the optical window. It was found that 6FB could have the optical window at the lower wavelength regions of the S-band (1480–1530 nm) and C-band (1530–1570 nm) but that of the PC at the higher wavelength regions of the C-band and L-band (1570–1610 nm). The present study provides another approach for designing new organic polymers for optical waveguides besides the current approach of reducing the C–H number density.
Optimal Design of Optically Gain-Clamped L-band Erbium-Doped Fiber Amplifier by Fiber Bragg Grating Method
Authors: Hsu Shih , Liang Tsair-Chun
Published: February 2005

We theoretically investigated the optimal design of optically gain-clamped (GC) L-band (1570–1610 nm) erbium-doped fiber amplifier (EDFA), in order to control the EDFA gain to ensure that the gain does not vary markedly in the presence of the add/drop of optical channels. It used a single fiber Bragg grating (FBG) on the input or output end of the erbium-doped fiber (EDF) to inject a portion of the amplified spontaneous emission (ASE) back into the system. The FBG center wavelengths (λB) at either 1565 or 1610 nm for optically gain-clamped operation of such L-band GC-EDFAs were examined. In addition, the different FBG bandwidths (ΔλB) for such L-band GC-EDFAs were compared. From the good gain-clamping capability point of view, the input-end FBG of 1565 nm center wavelength together with 4 nm bandwidth is the best choice for obtaining large gain-clamping dynamic ranges of good channel gain variation (ΔG) and fairly low noise figure characteristics.
Tailoring Photonic Strength in Monolithic Macroporous Silica for Random Media
Authors: Murai Shunsuke , Fujita Koji , Nakanishi Kazuki , Hirao Kazuyuki
Published: February 2005

A systematic method of tuning the photonic strength of disordered dielectric media has been demonstrated in monolithic silica (SiO2) with interconnected macropores prepared by the sol–gel method. Macroporous SiO2 gels are obtained in a system containing tetramethoxysilane, poly(ethylene glycol) (PEG), acetic acid, and water. The macroporous structure is formed when the transient structure of phase separation developed during the hydrolysis and polycondensation of alkoxysilane is chemically frozen-in by the sol–gel transition. The sizes of pores and skeletons, which are determined by the relative rate of phase separation to that of the sol–gel transition, can be controlled by the PEG content. The coherent backscattering measurement, together with the theoretical calculation based on the independent scattering approximation, reveals that the transport mean free path of light in the porous SiO2 can be tuned by adjusting the density and size of the pores.
Low-Temperature Sintering of B2O3-Added Ba(Mg1/3Nb2/3)O3 Ceramics
Authors: Lim Jong-Bong , Son Jin-ok , Nahm Sahn , Lee Woo-Sung , Yoo Myong-Jae , Gang Nam-Gi , Lee Hwack-Joo , Kim Young-Sik
Published: February 2005

The sintering temperature of Ba(Mg1/3Nb2/3)O3 (BMN) ceramic is about 1450°C. When B2O3 was added, BMN sintered at 900°C and it had a 1:2 ordered hexagonal structure. A liquid phase, which could be responsible for the decrease in sintering temperature, was observed in B2O3-added BMN. Mg4Nb2O9 and Ba2B2O5 second phases were found in the specimens and the Ba2B2O5 second phase might be related to the liquid phase. The dielectric constant (ε
r) and Q value increased with increasing sintering temperature and it is due to the increase in bulk density. However, they decreased with increasing B2O3 content, which can be explained by the existence of the second phases. Good microwave dielectric properties of Q ×f = 8500 GHz, ε
r = 27.5 and temperature coefficient of resonance frequency (τf) = 27.0 ppm/°C were obtained for BMN with 2.0 mol% B2O3 sintered at 930°C for 2 h.
Alumina Thick Films as Integral Substrates Using Aerosol Deposition Method
Authors: Nam Song-Min , Mori Naoko , Kakemoto Hirofumi , Wada Satoshi , Akedo Jun , Tsurumi Takaaki
Published: February 2005

Alumina thick films were fabricated by the aerosol deposition method (ADM) as integral substrates for integrated RF modules. By selecting a suitable powder and deposition conditions, alumina thick films as an integral substrate were successfully grown on glass and Al substrates at room temperature by the ADM. The relative dielectric permittivity and loss tangent of the alumina thick films on Al substrates were 9.5 and 0.005, respectively. To form microstrip lines on the aerosol-deposited alumina thick films, copper electroplating and lithography were employed, and a square-type cross section with sharp edges was obtained. Low-pass LC filters with a cutoff frequency of 10 GHz were simulated by electromagnetic analysis. The possibility of miniaturization of RF modules is proposed using alumina thick films fabricated by the ADM as an integral substrate.
Grating Based on Polymer-Stabilized Ferroelectric Liquid Crystal Films
Authors: Fuh Andy Ying-Guey , Mo Ting-Shan , Lin Chi-Huang
Published: February 2005

A surface-stabilized ferroelectric liquid crystal (SSFLC) film, doped with a small amount of monomer, BAB-6, was fabricated. The alignment performance and electrooptical effect of SSFLC films polymerized under different polarities of the DC field were examined. A grating was then fabricated by curing a doped SSFLC cell with UV through a photomask. The grating thus formed was found to be a combination of a phase grating and an amplitude grating, between which the grating could be switched by applying a suitable voltage. The response time was in the order of 500–600 µs.
Dielectric Properties of Frequency Modulation Twisted Nematic LCDs Doped with Palladium (Pd) Nanoparticles
Authors: Shiraki Hiroyuki , Kundu Sudarshan , Sakai Yoshio , Masumi Takenori , Shiraishi Yukihide , Toshima Naoki , Kobayashi Shunsuke
Published: February 2005

Twisted nematic liquid crystal display (TN-LCD) devices, composed of nematic liquid crystal (NLC), doped with palladium (Pd) nanoparticles, which are protected with the same NLC molecules of 5CB (Merck, K-15), show electrooptic characteristics that are featured by a frequency modulation and fast response. This device is called FM-TN-LCD. In this paper, we report that the frequency range in the FM-TN-LCD spreading from tens Hz to an upper limit 1 kHz, depending on the concentration of nanoparticles, correlates with that of the dielectric dispersion of the sample cell, which is expressed analytically by the Maxwell–Wagner theory on the heterogeneous dielectric medium, where the dielectric relaxation frequency, and thus the dielectric relaxation time, are primarily governed by the electrical conductivity of the doped nanoparticles of Pd and their concentrations.
Dielectric Properties of Frequency Modulation Twisted Nematic LCDs Doped with Silver Nanoparticles
Authors: Thisayukta Jirakorn , Shiraki Hiroyuki , Sakai Yoshio , Masumi Takenori , Kundu Sudarshan , Shiraishi Yukihide , Toshima Naoki , Kobayashi Shunsuke
Published: February 2005

Twisted nematic liquid crystal display (TN-LCD) devices, composed of nematic liquid crystal (NLC), doped with silver (Ag) nanoparticles, which are protected with the same NLC molecules of 5CB (Merck, K-15), show electrooptic characteristics that are featured by a frequency modulation and fast response. This device is called FM-TN-LCD. In this paper, we report that the frequency range in the FM-TN-LCD spreading from 40 Hz to an upper limit 2 kHz correlates with that of the dielectric dispersion of the sample cell, which is expressed analytically by the Maxwell–Wagner theory on the heterogeneous dielectric medium, where the dielectric relaxation frequency, and thus the dielectric relaxation time, are primarily governed by the electrical conductivity of the doped Ag nanoparticles.
Control of Thermally Enhanced Photoinduced Reorientation Direction of Photocrosslinkable Copolymer Liquid Crystals and Application to Polarization Gratings Using Linearly Polarized Ultraviolet Light
Authors: Kawatsuki Nobuhiro , Kuwabara Masaomi , Matsuura Yasushi , Ono Hiroshi , Emoto Akira
Published: February 2005

In this paper, we describe the thermally enhanced photoinduced reorientation behavior of copolymer liquid crystals, which comprise a methacrylate with 4-(4-methoxycinnamoyloxy)biphenyl (MCB) side groups and N-phenylmaleimide (PM), by irradiating with linearly polarized ultraviolet (LPUV) light and subsequent annealing. Adjusting the exposure energy controls the reorientation direction both perpendicular and parallel to the polarization of LPUV light. The generated birefringence is greater than 0.19 for both directions. A polarization grating with molecular orientation periodically modulated in orthogonal directions is fabricated using a grating photomask. The changes in the polarization of diffracted beams are similar to those of a polarization grating fabricated by a holographic technique.
Structural and Dielectric Properties of the BaTi5O11 Thin Film Grown on the Poly-Si Substrate using RF Magnetron Sputtering
Authors: Jeong Young-Hun , Jang Bo-Yun , Lee Suk-Jin , Sun Ho-Jung , Nahm Sahn , Lee Woo-Sung , Yoo Myong-Jae , Gang Nam-Gi , Lee Hwack-Joo
Published: February 2005

The BaTi5O11 thin films were grown on the poly-Si/SiO2/Si substrate using rf magnetron sputtering and their structural and dielectric properties were investigated. The BaO–TiO2 thin film deposited on the poly-Si substrate had an amorphous phase even though the growth temperature was high at 550°C. The crystalline BaTi5O11 thin films were formed when the amorphous film was annealed above 800°C. The BaTi5O11 phase was decomposed into Ba4Ti13O30, Ba2Ti9O20 and TiO2 phases as the films were annealed above 1100°C. The homogeneous BaTi5O11 thin film was formed when the film was grown at 550°C and rapid thermal annealed at 900°C for 3 min. The interface between the BaTi5O11 film and poly-Si substrate was sharp, and the inter-diffusions of the Si, Ba and Ti ions between the layers were negligible. The dielectric constant of the BaTi5O11 film was about 35, which is close to that of the bulk BaTi5O11 ceramics. The dissipation factor of all the films was smaller than 4.0%.
Performance Characterization of Thin AlN Films deposited on Mo Electrode for Thin-Film Bulk Acoustic-Wave Resonators
Authors: Tay Kok-Wan , Huang Cheng-Liang , Wu Long , Lin Meng-Shan
Published: February 2005

In this paper, we discuss the implementation and testing of a film bulk acoustic-wave resonator (FBAR) comprising an AlN piezoelectric thin film sandwiched between two metal electrodes and located on a silicon substrate with a low-stress silicon nitride (Si3N4) support membrane. In the present study, we choose molybdenum as the bottom electrode rather than the conventionally used Pt/Ti, Au/Cr or Al because it has a low acoustic attenuation and a good electrical conductivity, and provides a good adhesion between the thin AlN film and the low-stress Si3N4 membrane. We investigate the influence of AlN film thickness and top-electrode thickness on the resonance frequency of the FBAR device. The results indicate that decreasing the thickness of either the AlN film or the top electrode increases the resonance frequency. This suggests the potential of tuning the performance of the FBAR device by the carefully controlling AlN film thickness. Furthermore, it is also determined that the resonance frequency of the device can be increased by specifying a higher RF power for the magnetron sputtering process used to deposit the AlN film. This study employs an X-ray diffraction (XRD) technique to investigate the influence of AlN film thickness and RF power on the c-axis orientation of the thin film. It is shown that increasing either the thickness of the AlN film or the power of the RF sputtering process improves c-axis orientation. However, scanning electron microscopy (SEM) and atomic force microscopy (AFM) results reveal that a thicker AlN film exhibits a rougher surface and a larger grain size, both of which decrease the coupling factor of the FBAR device.
High-Resolution Scanning Tunneling Microscopy and Spectroscopy Studies of Deoxyribonucleic Acid and Fluorescein Isothiocyanate
Authors: Nojima Yoshihiro , Tanaka Hiroyuki , Yoshida Yuhsuke , Kawai Tomoji
Published: February 2005

By using scanning tunneling microscopy (STM), we obtained submolecular-resolution STM images of a single molecule of DNA labeled with the fluorescent dye fluorescein isothiocyanate (FITC). From the observed bias voltage dependences of the topographic height and I–V characteristics of FITC and the single molecule DNA, we found that FITC and DNA have different electrical properties. This study shows that STM is useful in the analysis of the properties of molecules by the investigation of a single molecule.
Ultrasound Inverse Scattering Computed Tomography under the Angular Illumination Limitation
Authors: Yamada Akira , Yano Satoshi
Published: February 2005

Transmission ultrasound inverse scattering computed tomography is expected to be useful for breast cancer screening, because it provides the quantitative sound speed reconstruction of tissue properties. For the realization of the system, however, large-scale ring array acquisition systems are required and hardware cost becomes very high. To resolve this problem, four linear array probes are placed around the rectangular perimeter of the target region. By this means, system may be realized at a lower cost and may still be compatible with conventional B mode imaging. In this system, a limitation on the illumination angle is imposed based on the range achievable with electronic scanning by the four linear arrays. Hence, ill-posedness caused by the lack of angular view information becomes a serious problem. As a resolution to this problem, a hybrid method using both angular and frequency diversity observations is employed, so that low-frequency scattering signal components are incorporated into the image reconstruction calculations. To examine the method numerically, scattered data are synthesized for tissue-like rectangular test objects through rigorous calculations using the finite difference method. From the results of the reconstructed images, it is demonstrated that the precision of the sound speed and reproducibility of the object shape is almost satisfactory, even when the illumination view is limited over an extremely narrow range.
Effects of Source Pulse Shape on Low-Frequency-Sound Propagation
Authors: Naoi Jun , Tsuchiya Toshio , Kikuchi Toshiaki
Published: February 2005

We studied the degradation of the source pulse form in long-range propagation of low-frequency sound in the sound fixing and ranging (SOFAR) channel in the ocean. We made the numerical simulation of the source pulse propagation with changing the parameters of the simulation; carrier frequency, source pulse width, and propagation range. In long-range propagation such as 1000 km, 2000 km and 3000 km, there are a limited number of combination of the frequency and the pulse width for minimizing the consequent pulse degradation. These results are applicable to the design of the actual ocean propagation experiment itself and also of sound source equipment for the experiments.
Beam Test of Multi-Bunch Energy Compensation System in the Accelerator Test Facility at KEK
Authors: Kashiwagi Shigeru , Hayano Hitoshi , Kubo Kiyoshi , Korhonen Timo , Nakamura Shogo , Naito Takashi , Oide Katsunobu , Takeda Seishi , Terunuma Nobuhiro , Urakawa Junji
Published: February 2005

A beam test of the multi-bunch energy compensation system (ECS) was performed using the ΔF method with the 2856±4.327 MHz accelerating structures in the accelerator test facility (ATF) at KEK. The 1.54 GeV S-band linac of the ATF was designed to accelerate a multi-bunch beam that consists of 20 bunches with 2.8 ns spacing. The multi-bunch beam with 2.0×1010 electrons/bunch has an energy deviation of about 8.5% at the end of the linac due to transient beam loading without ECS. The ATF linac is the injector of the ATF damping ring (DR), whose energy acceptance is ±0.5%. The beam loading compensation system is necessary in the ATF linac for the successful injection of multi-bunch into DR. The rf system of the linac consists of 8 regular rf units with the SLED system and 2 ECS rf units without the SLED system. The accelerating structures of the regular units are driven at 2856 MHz and the 2 ECS structures are operated with slightly different rf frequencies of 2856±4.327 MHz. In the beam test, we have succeeded in compressing the multi-bunch energy spread within the energy acceptance of the DR using ΔF ECS. The principle of the beam loading compensation system of KEK-ATF and the experimental results are described in this paper.
Nanopatterning of Si Substrate Using Nanospheres as a Mask for Localized Anodization
Authors: Asoh Hidetaka , Uehara Aya , Ono Sachiko
Published: February 2005

A silicon oxide nano-honeycomb structure and an ordered Si convex array have been fabricated using self-assembled polystyrene beads as a mask for localized anodization and the subsequent chemical etching. The silicon oxide nano-honeycomb structure, which could be produced only on the exposed Si surface, that is, a triangular void among the three spheres on the substrate, was fabricated using electrochemical oxidation. On the other hand, the silicon convex hexagonal array was fabricated by selective chemical etching of the oxide honeycomb pattern in hydrogen fluoride. The dimensions of the obtained nanostructures could be controlled arbitrarily by changing the diameter of the nanospheres used as a mask.
Replication Technology for Micro/Nano Optical Components
Authors: Kang Shinill
Published: February 2005

Micro/nano replication processes, including micro/nano thermal forming (compression molding and hot embossing), UV-molding, micro injection molding, and glass micro molding are regarded as the most promising mass-production methods for micro/nano optical components because they offer high repeatability, mass producibility with low-cost and versatility in terms of molding material selection. To replicate micro/nano optical components, it is required to prepare the mold inserts that have the cavities of the same shape as the components. One can use any established methods to make mold, such as direct machining, wet etching, dry etching, electroforming, compaction and sintering, and so on. This paper reviews the general issues on mold fabrication and replication technologies for micro/nano optical components with our recent work and results in these areas.
All-Optical Switching and Wavelength Conversion Based on Ultrafast Nonlinearities in Semiconductor Optical Amplifiers
Authors: Dorren Harm J. S. , Mishra Arvind K. , Yang Xuelin , Li Zhonggui , Ju Heongkyu , Waardt Huug de , Khoe Djan , Lenstra Daan
Published: February 2005

We investigate all-optical switching and wavelength conversion based on ultrafast nonlinearities in a multi-quantum-well semiconductor optical amplifier. We present a rate equation model that accounts for two-photon absorption, free-carrier absorption, self- and cross phase modulation, carrier heating, spectral, spatial hole burning and self- and cross polarization modulation. We demonstrate optical AND gate operation using a semiconductor optical amplifier placed in an asymmetric March-Zehnder interferometer and we show that the gate can be operated using 800 fJ optical pulses with duration of 200 fs. We also investigate wavelength conversion based on ultrafast nonlinear polarization rotation. We found a conversion efficiency of 12 dB for control pulse energies of 10 pJ.
Design and Analyses of a Planar Zoom Module as a Beam Expander
Authors: Wei An-Chi , Shieh Han-Ping D.
Published: February 2005

A novel planar zoom module (PZM) is presented in this article. The PZM is realized by integrating optical elements on its surfaces with the folding optical axis and performing the zoom function by transversal rotation or motion. Its application as a multimagnification beam expander is designed, analyzed, and demonstrated.
Design and Fabrication of Grating Demultiplexer Using Hollow Optical Waveguide
Authors: Ishikawa Mayumi , Miura Toru , Matsutani Akihiro , Koyama Fumio
Published: February 2005

We present the design and fabrication of a grating demultiplexer with a hollow optical waveguide. The use of a hollow optical waveguide enables temperature-insensitive operations as well as wavelength tunability with the help of microelectro-mechanical system (MEMS) technology. We present the design of a compact reflective concave grating demultiplexer using a hollow optical waveguide whose wavelength resolution is less than 1 nm. In order to reduce the insertion loss, we use a hollow optical waveguide with either metal thin-film coating or dielectric multilayer mirror. We fabricate Au-coated hollow waveguide grating demultiplexers with various device lengths. We measure the spectral response from the fabricated demultiplexers, exhibiting a possibility of high wavelength resolution of below 1 nm. We also present the evaluation of multi-channel operations using a fabricated demultiplexer.
Vertically Coupled Microring Resonator Filter with Multilevel Crossing Busline Waveguide
Authors: Hanai Takamitsu , Suzuki Shuichi , Hatakeyama Yutaka , Kokubun Yasuo
Published: February 2005

We have proposed and demonstrated a vertically coupled microring resonator filter as an add/drop filter.In this waveguide filter, a microring resonator is stacked at the crossing point of the cross grid busline waveguide. However, since the scattering loss at the crossing point of the busline waveguide is 0.2 dB/point, the integration scale is limited to be less than several tens to a hundred. Thus in this study, the scattering loss at the crossing points of busline waveguides in the vertically coupled microring resonator filter was eliminated by a multilevel crossing structure of busline waveguides. The top surface of each buried waveguide was perfectly planarized by a new fabrication process and clear filter responses were observed for single-ring and double-series-coupled ring resonators with multilevel crossing busline waveguides.
Integrated Reciprocating Optical Modulator for Optical High-Order Sideband Generation
Authors: Kawanishi Tetsuya , Yoshiara Kiichi , Oikawa Satoshi , Shinada Satoshi , Sakamoto Takahide , Izutsu Masayuki
Published: February 2005

We demonstrated optical high-order sideband generation using a reciprocating optical modulator consisting of a pair of fiber Bragg gratings and an optical phase modulator. The reflection band of the fiber Bragg grating had a steep edge of 0.02 nm. A twelfth optical high-order sideband component was generated from a 4.4 GHz electric signal. Millimeter waves generated as beat signals of the optical high-order sideband components were quite stable. Spectrum line widths were less than 300 Hz. The intensity modulation of the generated millimeter waves was also demonstrated by applying a baseband signal to the modulator without using another electric or optical modulator.
Polysilane/Polysilazane Composite: Novel Material for Optical Waveguides and Its Application to Mode-Conversion Filters
Authors: Mataki Hiroshi , Yamaki Shigeru , Fujiki Tsuyoshi , Kawasaki Shin-ichi , Tanabe Nobuyasu , Okayama Hideaki , Nakajima Hirochika
Published: February 2005

Polysilane/polysilazane (PS/PSz) composite is proposed as a novel material for optical waveguides. A refractive index change, as large as about 4.5%, can be induced and automatically built in only by UV exposure without etching and/or development due to a photochemical reaction, generally known as “photobleaching”. To verify the practical performance of the PS/PSz composite for photonic devices with refractive-index-modulated structures, we fabricated optical waveguide mode-conversion filters using polymethylphenylsilane (PMPS)/perhydropolysilazane (PHPSz) composite, and successfully demonstrated its operation in both visible (633 nm) and infrared (1310 nm) wavelength ranges. The result shows that the PS/PSz composite is a promising candidate not only for optical waveguide devices such as those used in CWDM applications, but also for optical interconnections.
Sum-Frequency Generation in Periodically Poled KTiOPO4 with Large Tolerances of Temperature and Wavelength
Authors: Furukawa Yukio , Sakata Hajime , Yagi Takayuki
Published: February 2005

In a sum-frequency generation system based on periodically poled nonlinear optical crystal, a new approach to the expansion of acceptance widths of temperature and wavelength has been demonstrated. By using periodically poled KTiOPO4 (PPKTP), the condition is found theoretically so that the tolerances of temperature and wavelength are enlarged. A temperature acceptance width of 60°C is obtained experimentally by mixing the light of two diode lasers (1590 nm and 808 nm) in a 10-mm-long PPKTP crystal.
A Practical Laser Projector with New Illumination Optics for Reduction of Speckle Noise
Authors: Kasazumi Ken'ichi , Kitaoka Yasuo , Mizuuchi Kiminori , Yamamoto Kazuhisa
Published: February 2005

We have developed illumination optics for image projection systems. It realizes uniform illumination and suppression of speckle and diffraction noises by using a diffuser and integrator optics. By optimizing the diffusing angle of the diffuser, optical power loss was less than 10%. A proto type of a laser projector with a red wide-stripe semiconductor laser and green and blue second-harmonic generation lasers was realized by using the developed illumination optics and twisted nematic liquid-crystal panels. Still images from a personal computer and video images from a digital versatile disk (DVD) player were displayed with the system and a wide colour gamut and smooth images without diffraction noise nor speckle noise were confirmed.
Short-Circuit Destruction of Field-Stop-Structure Inslated Gate Bipolar Transistor
Authors: Yoshikawa Koh , Koga Takeharu , Fujii Takeshi , Nishiura Akira , Matsuda Akinori , Matsumoto Takashi
Published: February 2005

Numerical and experimental results of the field stop (FS) and lifetime control (LC) IGBT short-circuit characteristics using 4500 V-class devices are described. During the short-circuit condition, avalanche breakdown occurs along the base/FS layer interface. This is because the strength of the electric field becomes high due to the increase in the majority carrier concentration, which is larger than the impurity concentration in the base layer. The lower current gain in the device results in a higher electric field. It can be concluded that FS-IGBT has a narrower short circuit safety operating area (SCSOA) than other devices. Particularly, this phenomenon is easy to show on the high-voltage-class device, such as a 4.5 kV IGBT, because its impurity concentration in the base layer is low.
Electromigration-Induced Void Growth Kinetics in SiNx-Passivated Single-Damascene Cu Lines
Authors: Yokogawa Shinji
Published: February 2005

Basic electromigration characteristics of SiN
x
-passivated single-damascene Cu lines have been investigated. The results indicate that an effective incubation time for void growth contributes to resistance change. This effective incubation time depended inversely on the square of current density. The activation energy of the effective incubation time was 1.14 ±0.27 eV. The observed critical product of electromigration was approximately 5900 A/cm. The activation energy of diffusion was 0.89 ±0.07 eV. These results indicate that the Cu/SiN
x
interface diffusion activation energy and the effective charge number are similar to those of unpassivated Cu surface diffusion. However, the SiN
x
-passivated interface of the sample showed significantly reduced drift velocity compared to those of the unpassivated sample.
Novel Reconfigurable Logic Gates Using Spin Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Matsuno Tomohiro , Sugahara Satoshi , Tanaka Masaaki
Published: February 2005

We propose and numerically simulate novel reconfigurable logic gates employing spin metal-oxide-semiconductor field-effect transistors (spin MOSFETs). The output characteristics of the spin MOSFETs depend on the relative magnetization configuration of the ferromagnetic contacts for the source and drain, that is, high current-drive capability in parallel magnetization and low current-drive capability in antiparallel magnetization [S. Sugahara and M. Tanaka: Appl. Phys. Lett. 84 (2004) 2307]. A reconfigurable NAND/NOR logic gate can be realized by using a spin MOSFET as a driver or an active load of a complimentary MOS (CMOS) inverter with a neuron MOS input stage. Its logic function can be switched by changing the relative magnetization configuration of the ferromagnetic source and drain of the spin MOSFET. A reconfigurable logic gate for all symmetric Boolean functions can be configured using only five CMOS inverters including four spin MOSFETs. The operation of these reconfigurable logic gates was confirmed by numerical simulations using a simple device model for the spin MOSFETs.
Design of Superconducting Quantum Interference Device for Magnetic Immunoassays
Authors: Enpuku Keiji , Ohba Akihiro , Inoue Katsuhiro , Soejima Kazuyuki
Published: February 2005

A superconducting quantum interference device (SQUID) for application to biological immunoassays has been designed. In this application, the magnetic field from a magnetic marker made of magnetic nanoparticles is detected with the SQUID. It is shown that the conventional design of the SQUID that was developed for the case of uniform magnetic field cannot be used in this application, since the spatial variation of the magnetic field from the marker is large. Therefore, a numerical simulation method is developed for obtaining a signal flux detected with the SQUID when the magnetic field changes spatially. It is shown that the signal flux strongly depends on the geometrical parameters of the measurement system, such as the size of the pickup coil, size of the sample and the distance between the sample and the SQUID. The dependence of the signal flux on these geometrical parameters is quantitatively clarified, and the optimum design of the SQUID for the application to magnetic immunoassays is discussed.
Field Dependence of Strain Imaging in Magnetic Observation of Ferrite Head
Authors: Takata Keiji , Tomiyama Futoshi , Shiroishi Yoshihiro
Published: February 2005

When a magnetic material was subjected to an external magnetic field, a strain was generated in the material and the strain was detected and imaged with a scanning probe microscope. The images obtained with unipolar fields, however, were quite different from those obtained with bipolar fields. We discuss the magnetic field dependence of magnetic strain imaging and propose a physical interpretation. We conclude that strains are magnetostrictive in weak fields, and are mainly caused by magnetic forces in strong fields. The images obtained with unipolar fields represent domain structures at the peak fields, and those with bipolar fields represent the distribution of asymmetry of magnetization reversal.
Characteristics of Laser Diode Bar and Stack with Jet-Type, Water-Cooled Heatsink
Authors: Miyajima Hirofumi , Kan Hirofumi , Furuta Shin-ichi , Uchiyama Takayuki , Oishi Satoru , Yamanaka Masanobu , Izawa Yasukazu , Nakai Sadao
Published: February 2005

Our group has developed a funryu (“fountain flow” in Japanese) heatsink structure for a 1 cm laser diode (LD) bar. The funryu heatsink is only 1.1 mm in thickness and is designed in stackable form. With the help of a good indium soldering technique and detailed thermal analysis, this device achieved a thermal resistance of only 0.25°C/W, defined by the temperature increase per unit of heat dissipation. This thermal resistance is one of the lowest ever attained by a laser diode bar. By stacking 30 LD bars equipped with these funryu heatsinks, we achieved a CW output power of 2.3 kW from a 10 mm×45.8 mm laser-emitting area within the stacked-LD module. This power intensity corresponds to 502 W/cm2.
Enhancing the Overwriting Characteristics of Phase-Change Optical Disks by Doping in Dielectric Layers
Authors: Yu Chien-Hui , Hsieh Tsung-Eong , Yeh Tung-Ti , Shieh Han-Ping D.
Published: February 2005

In this work, we studied the enhancement of overwriting characteristics of phase-change optical disks by doping in the dielectric layers. The doping elements included chromium (Cr), molybdenum (Mo), nickel (Ni), tantalum (Ta), titanium (Ti), tungsten (W), vanadium (V), and nitrogen (N2). Dynamic test showed that doping with a certain amount of W and N2 in dielectric layers enhanced the disk overwriting characteristics. Up to fortyfold improvement in disk cycleability was observed when N2 gas was introduced during sputtering deposition of the upper dielectric layer at the gas flow rate of N2/Ar=25%. Tungsten was the best among the doping metallic elements resulting in fivefold improvement in disk cycleability. Optical property measurement revealed that the refractive index (n) decreased with increasing N2 doping percentage, while the relatively small amount of metallic element doping negligibly changed the optical constants. Subsequent modulation simulation showed that such an optical property change is beneficial to disk overwriting characteristics. Nanoindentation test showed that N2 doping was the most effective method for increasing the hardness of the dielectric layer. This implies that, with increasing mechanical strength, the dielectric layer possesses better resistance to thermal deformation resulting from laser heating, thereby enhancing the cycleability of optical disks.
Selection from Complex Self-Pumped Phase-Conjugated Images
Authors: Ichinose Masafumi , Miyakawa Kazuhiro , Yamashita Masafumi
Published: February 2005

Two methods for the extraction of specific information from complex self-pumped phase-conjugated images are presented. Barium titanate is employed as a self-pumped phase-conjugated mirror. Extraction by adjusting the screen position to the desired sample is shown to be effective when the individual samples are spaced at discrete intervals, while vibration of the sample is effective when the samples are set in a compact sequence. These methods allow a single image to be extracted from complex images when coupled with digital post-processing.
Effect of Optical Fiber Output Surface on Laser Induced Shock Wave and Its Application
Authors: Nose Hidetoshi , Maeda Hiroshi , Yamamoto Noriyasu , Nakahara Motonao
Published: February 2005

A high-pressure pulse is produced from an optical fiber output surface under the application of a pulsed laser. We found that enhancement of the absorption of laser energy due to the generation and growth of plasma takes place at the output surface, if the surface is intentionally roughened. The effect of roughness causes the pressure enhancement of the generated shock wave in water. We also found high pressure shock wave propagation in water from the fiber on which the output surface was roughened and rounded intentionally. These measures further enhance the shock wave generation. These enhancement phenomena due to the roughness and the round shape can be used as a controllable pressure pulse source for microsurgery in medicine. They have been observed by means of pulsed laser shadowgraphy. The shock wave propagation characteristics are found to depend upon various parameters such as the fiber diameter, the fiber material, the surface roughness, the surrounding medium, and the laser energy. As an example of the application of shock wave propagation, an experiment in cutting gelatin by means of the shock wave was carried out. The cross section of gelatin is strongly dependent on the pulse duration time width of the laser. When the duration time is 1.7 µs, the gelatin was cut most deeply.
Design of Light-Diffusing Film for Full-Color Reflective Liquid Crystal Display with High Contrast and Wide Viewing Angle
Authors: Ishinabe Takahiro , Nakayama Takanori , Miyashita Tetsuya , Uchida Tatsuo
Published: February 2005

Reflective liquid crystal displays (LCDs) attract considerable interest for being light and having low power consumption. We proposed a new type of reflective LCD mainly comprising a hybrid-aligned nematic LC layer, biaxial retardation films, a light-diffusing film and a mirror electrode. This new type of reflective LCD has the advantages of high resolution owing to the mirror electrode and wide viewing angle because it is designed using the same concept as the OCB mode. In this paper, we describe the optimum conditions for the light-diffusing film used in this new reflective LCD.
Observation of Carrier Behavior in Organic Photoconductor by Transient Space-Charge Measurement
Authors: Hozumi Naohiro , Iwakiri Akihiko , Nagao Masayuki , Hashimoto Yuichi , Fukunaga Kaori
Published: February 2005

Space-charge measurement by an acoustic technique such as the pulsed electroacoustic method has often been applied to insulating materials with low carrier mobility. However, some functional materials have high carrier mobility so that the evolution of space charge is difficult to observe. In this study, a new measurement method which can measure the rapid transient of space charge was proposed and applied to a photoconductive material. The space charge after the illumination by a light pulse was traced with an interval of several hundred microseconds. It was observed that a charge packet traveled through the material after being generated at the illuminated side. The behavior was interpreted into the average carrier mobility. The mobility was in good agreement with that obtained by the conventional time-of-flight method using a transient current.
Energy Harvesting Using a Piezoelectric “Cymbal” Transducer in Dynamic Environment
Authors: Kim Hyeoung Woo , Batra Amit , Priya Shashank , Uchino Kenji , Markley Douglas , Newnham Robert E. , Hofmann Heath F.
Published: February 2005

In this study, we investigated the capability of harvesting the electrical energy from mechanical vibrations in a dynamic environment through a “cymbal” piezoelectric transducer. Targeted mechanical vibrations lie in the range of 50–150 Hz with force amplitude in the order of 1 kN (automobile engine vibration level). It was found that under such severe stress conditions the metal–ceramic composite transducer “cymbal” is a promising structure. The metal cap enhances the endurance of the ceramic to sustain high loads along with stress amplification. In this preliminary study, the experiments were performed at the frequency of 100 Hz on a cymbal with 29 mm diameter and 1 mm thickness under a force of 7.8 N. At this frequency and force level, 39 mW power was generated from a cymbal measured across a 400 kΩ resistor. A DC–DC converter was designed which allowed the transfer of 30 mW power to a low impedance load of 5 kΩ with a 2% duty cycle and at a switching frequency of 1 kHz.
Triangular Current: Method for Measuring Hysteresis Loops of Ferroelectric Capacitors
Authors: Wang Ding-Yeong , Chang Chun-Yen
Published: February 2005

In this paper, we present a triangular current (TC) method for measuring the hysteresis loops of Pb(Zr,Ti)O3 capacitors prepared on Pt/Ta/SiO2/Si substrates. Like the constant current (CC) method, this method is a current source mode method for obtaining hysteresis loops. By applying a triangular charging current to a specimen, a measured voltage profile, which is almost noiseless and smooth in the high-field region, is obtained and its hysteresis curve can be determined using integral calculus to convert the charging current to charge. Under various charging conditions, the similarity of the obtained hysteresis curves implies that the step charging current and number of steps do not affect the measured results. Moreover, the parasitic effect of the probe setup is found to possibly increase the maximum polarization of the ferroelectric capacitor as the area of the capacitor is reduced. The TC method can be utilized to determine the parasitic capacitance of the probe setup and then can easily determine the corrected hysteresis loops of small capacitors. These findings reveal that the TC method constitutes a new method for measuring the hysteresis loops of ferroelectric capacitors.
Modulated Structure of Misfit Layered Cobalt Oxide [(Ca0.90Bi0.10)2(Co0.95Bi0.05)O3]pCoO2
Authors: Miyazaki Yuzuru , Suzuki Yousuke , Onoda Mitsuko , Ishii Yoshinobu , Morii Yukio , Kajitani Tsuyoshi
Published: February 2005

We have determined the crystal structure of Bi-substituted and Bi-free misfit layered cobalt oxides [Ca2CoO3]0.62CoO2, by a (3+1)-dimensional superspace group approach. Structural parameters have been refined with a superspace group of C2/m(1p0)s0 using powder neutron diffraction data. Bismuth atoms are found to substitute for both Ca and Co atoms in the rock salt-type [Ca2CoO3] subsystem. The resulting structural formula is expressed as [(Ca0.90Bi0.10)2(Co0.95Bi0.05)O3]
p
CoO2 with a refined b-axis ratio of p=0.6183. By Bi substitution, the modulation of the Co–O distances in the [Ca2CoO3] subsystem is markedly decreased relative to the Bi-free counterpart, whereas such a modulation in the [CoO2] subsystem is slightly increased. The observed increase in the Seebeck coefficient and electrical resistivity of the Bi-substituted phase can be explained in terms of the decrease in hole concentration in the CoO2 sheets.
Effect of Grain Curvature on Nano-Indentation Measurements of Thin Films
Authors: Tsai Kuang-Yue , Chin Tsung-Shune , Shieh Han-Ping D.
Published: February 2005

Grain curvature effect on the measurement of nano-indentation has been observed for the first time, taking VO2 thin film as an example. As the grain size of thin film is comparable to the diameter of indenter tip, the maximum penetration depths under the same maximum load (P
max) vary and lead to deviations in estimated hardness and Young's modulus. Under the same P
max, larger penetration depth leads to a larger projected area, and a decrease in hardness. The large deviation of stiffness, affected by surface roughness under low P
max, produces fluctuation of Young's modulus. Increase in penetration depth diminishes the roughness effect so that deviations in penetration depths dominate the variations in Young's modulus. The hardness and Young's modulus curves measured at lowest penetration depth, being thought to be free from effect of grain curvature, coincide very well to the curves measured by continuous stiffness measurements mode.
In-situ Optical Spectroscopy of Ablation Plume for Preparations of Nanostructured TiO2 Thin Films by Pulsed Laser Deposition
Authors: Kitazawa Sin-iti
Published: February 2005

Nanostructured TiO2 thin films on α-Al2O3 (0001) substrates prepared by pulsed laser deposition (PLD) were analyzed and evaluated in terms of the buffer O2 gas pressure (0–80 Pa) dependencies by optical spectroscopy and surface morphology. Optical emission spectra of the ablation plume from Ti and TiO2 targets were measured in-situ. The contribution from TiO molecules was observed by narrow-band photometry. The surface morphology was observed by an atomic force microscope (AFM), revealing the pressure dependence of nanostructures. The crystalline structures of prepared TiO2 thin films were observed by X-ray diffraction (XRD). The optically observed band-gaps of the prepared thin films show that the crystal structures are mixed crystals of rutile and anatase. Evaporated Ti particles combine with buffer O2 gas thereby producing TiO molecules, which affect the formation of nanostructures on TiO2 thin films.
Fabrication of Gold Nanowires Using Contact Mode Atomic Force Microscope
Authors: Watanabe Manabu , Minoda Hiroki , Takayanagi Kunio
Published: February 2005

Gold nanowires were fabricated using a contact mode atomic force microscope (AFM), the tip of which scans a thin gold layer predeposited on a mica substrate. The nanowires are spaced with an interval in the range of 130–590 nm. Their widths and heights are distributed in the range of 70–110 nm and 4–7 nm, respectively. By adjusting the strength of the force applied by the AFM tip, the spacing, width and height of the nanowires can be controlled and made to increase as the applied force increases. Scanning an extensional area enabled us to fabricate long nanowires.
Bubble Evolution and Radiation Mechanism for Laser-Induced Collapsing Bubble in Water
Authors: Byun Ki-Taek , Kwak Ho-Young , Karng Sarng Woo
Published: February 2005

Bubble behavior and the radiation mechanism from a laser-induced collapsing bubble were investigated theoretically using the Keller–Miksis equation for the bubble wall motion and analytical solutions for the vapor inside the bubble. The calculated time-dependent bubble radius is in good agreement with observed ones. Also, the calculated half width and the total emission of the luminescence pulse from the vapor bubble at the collapse point agreed well with the observed value of 8 nanoseconds and 2.3 mW, respectively. The inert gas content inside the laser-induced vapor bubble was too small to produce light emission due to bremsstrahlung.