bluuebunny/crossref_metadata_2025_split huggingface dataset:
Boundary element analysis of electromagnetic fields in cylindrical structures
Authors: Matsuhara Masanori , Kamura Masahiro , Maruta Akihiro 
Published: July 2007

AbstractA novel combined integral equation, which is adaptable to the analysis of a general electromagnetic field in a cylindrical structure, is proposed. The unknown quantities of the equation are the transverse electromagnetic field components and the equation is analyzed numerically by the boundary element method. The combined integral equation does not have the difficulty arising from the nonphysical solutions which have been troubled conventionally. In addition, the integral equation does not contain spatial derivatives of the unknown quantities. The coefficient matrix of the matrix equation obtained by the application of the boundary element method is square and is hence suitable for numerical analysis.In this paper, first the combined integral equation for unknown transverse electromagnetic field components are derived. The uniqueness of the solution is proven. Further, the integral equation is analyzed numerically for actual examples by the boundary element method so that the validity and effectiveness of the method are verified.
A method for the design of dielectric multilayer bandpass filters
Authors: Miyauchi Kazuhiro , Wakabayashi Isamu 
Published: July 2007

AbstractA design method of a dielectric multilayer bandpass filter for optical‐communication is proposed, and its feasibility is demonstrated for an example of the design.The design procedure is to replace each resonator in a specified LC bandpass filter by a corresponding dielectric multilayer resonator. This LC bandpass filter is obtained from an LC lowpass prototype through a frequency transformation. New structures of a dielectric multilayer resonator are proposed, and the equations necessary for the design are derived. A method to correct a design error due to excess phase also is discussed.With the present design method, an arbitrary polynomial characteristic (Butterworth, Chebyshev, and Bessel, etc.) can be realized as a dielectric multilayer bandpass filter. A good agreement is found between the designed and actual performance for a narrowband bandpass filter.
A liquid sensor based on a shear horizontal saw device
Authors: Kondoh Jun , Shiokawa Showko 
Published: July 2007

AbstractThe surface acoustic wave (SAW) changes its propagation characteristic if the region above the propagation surface is altered. This phenomenon can be used for realization of an SAW sensor. The Rayleigh mode known as a general SAW can be used as a gas phase sensor. If, however, the propagation surface is loaded with liquid, a longitudinal wave is radiated into the liquid and the Rayleigh wave decays. Hence, this wave cannot be used for a liquid sensor.To realize a liquid sensor, the SH mode must be used in which the particle displacement is normal to the propagation direction and parallel to the propagation surface. It has been reported that the SAWs propagating on piezoelectric crystals such as 36° rotated Y‐cut X propagation LiTaO3and X‐cut 150° propagation LiTaO3are SH‐mode SAWs (SH‐SAW).In this paper, it is found theoretically and experimentally that the shear horizontal‐ (SH‐) SAW devices using these piezoelectric crystal cannot only detect the mechanical effects such as the viscosity of the liquid and the mass loading in the liquid but also the electrical effects such as the permittivity and conductivity of the liquid. By way of comparison with other liquid sensors using high‐frequency ultrasonic devices, the characteristics of the SH‐SAW sensors are clarified.
Films of the intermetallic compound CuTi2 and their applications in Cu/CuTi2/Si contact structures
Authors: Yoshimoto Ken'ichi , Sasaki Takahiro , Sasaki Katsutaka , Noya Atsushi 
Published: July 2007

AbstractTo prepare constituent materials applicable to a Cu metallization technology of Si‐LSI, the preparation conditions of Cu‐Ti intermetallic compound films have been examined and the thermal stability of the Cu/CuTi2/Si contact structure has been studied using CuTi2 compound films as a diffusion barrier. As a result, a stoichiometric intermetallic compound film of CuTi2 was prepared successfully at a substrate temperature of 300°C by dc sputtering using a composite target with an area ratio of Cu : Ti = 51 : 49.From the study on the CuTi2/Si contact structure, it was revealed that the CuTi2 phase was stable up to 500°C and a thin interface layer of Ti silicide was formed at the interface of CuTi2/Si but the excess diffusion and/or reaction have not been observed. Ti silicide layer formed at the interface is believed to be effective for low contact resistance. To examine whether or not CuTi2 films are suitable for Cu metallization technology, the thermal stability of Cu/CuTi2/Si contact structure was examined. It was found that the structure is successfully stable up to 500°C and is useful for Cu metallization technology. The reason is believed to be as follows: the interface of Cu/CuTi2 is in the chemical equilibrium state and CuTi2 itself is a stable compound phase at high temperatures in the Cu‐Ti alloy system.
Preparation of sintered acicular ba‐ferrite particles and determination of their magnetic properties
Authors: Fujita Minoru , Ueda Tetsuya , Hiratsuka Nobuyuki 
Published: July 2007

AbstractAcicular barium ferrite fine particles were successfully fabricated by sintering a mixture of Ba(OH)2 8H2O and acicular α‐FeOOH at a temperature of 500 to 1200°C for 1 hr in air and then rapidly cooled down. For sintering temperatures below 800°C, no magnetization was found. However, with increasing temperature beyond 900°C, the magnetization increased significantly in accordance with the formation of hexagonal barium ferrite. The coercivity increased for sintering at 900 to 1000°C and then decreased at 1100 to 1200°C where a significant grain growth was observed.Acicular barium ferrite fine particles with an atomic ratio 1 : 10 between Ba and Fe ions sintered at 1000°C were found to consist of particles of about 0.7‐μm length and an aspect ratio of about 7, which exhibit the magnetization and coercivity of 61 emu/g (61 A.m2/kg) and 3990 Oe (317.5 kA/m), respectively. Coated‐films were fabricated by dispersing barium ferrite fine particles thus obtained in resin solution, which were then coated onto polyester films.The squareness ratio of nonoriented films for the vertical field direction is larger than that for acicular barium ferrite fine particles, and the films were more easily magnetized along the film normal. When the magnetic field was applied along the film normal at the time of drying the film, the sample can easily be magnetized also. This result seems to indicate the possibility of barium ferrite‐coated films for vertical magnetic recording media. The major axis of acicular barium ferrite fine particles was found to be in the film plane and the easy axis for magnetization is along the film normal.
Complex eigenstates of an electron in quantum box structures in the presence of an external electric field
Authors: Tsuji Yasuhidé , Hayata Kazuya , Koshiba Masanori 
Published: July 2007

AbstractAs a useful approach to analyze the eigenstate of electrons inside a quantum box, the weighted potential method (WPM), already proven to be valid in a one‐dimensional system (wire structure), is applied to the zero‐dimensional one (box structure). The formulation and analysis were made for the quantum box structure of a finite potential barrier height in the presence of an applied electric field.The analysis, which takes into account the tunneling effect of electrons through the barrier when the electric field becomes strong, was carried out for the eigenstates. The method allows us to estimate the electron lifetime. A discussion also was made for an actual structure in which the effective mass of electrons is changed from a quantum well to a barrier region. The change in the eigenenergy was found to become more significant when increasing the number of the quantized direction.
Performance improvement in digital magnetic recording by write and read equalization
Authors: Okamoto Yoshihiro , Osawa Hisashi , Takigawa Kiyoshi , Ono Kazuo 
Published: July 2007

AbstractDC‐freeing of write waveform is an important technique in digital magnetic recording. In this paper, it is achieved by using write equalization, which is one of the dc‐freeing methods, and on the read side, read equalization, which not only can reduce high‐frequency noise but also has little degradation of eye opening. A new write and read equalization method developed by investigating it from a synthetic viewpoint is proposed along with a signal detection method which brings out the best in the equalization method.First, it is shown that it is possible to dc‐free by the write equalization and then a read equalization and signal detection method is described which enables high signal‐to‐noise ratio (SNR) to be obtained by combining with the write equalization. Furthermore, it is clarified by computer simulation that our proposed system shows an excellent error rate performance compared with the combination of NRZ recording code and integrated detection, which is well known for its good performance so far.
A current‐mode multivalued logic circuit based on by Bi‐CMOS transistors
Authors: Ueno Fumio , Inoue Takahiro , Sasaki Mamoru , Taniguchi Kazutaka , Yamashita Toshitsugu 
Published: July 2007

AbstractThis paper proposes a Bi‐CMOS current‐mode multivalued logic circuit enabling high‐accuracy computation, high‐speed computation, and high integration. In conventional current‐mode multivalued logic circuits using I2L and CMOS configurations, the realization of high‐radix multivalued logic circuits was difficult due to the calculation errors in the basic circuits, such as a current mirror or subthreshold detector.As a result of simulations of the basic circuits proposed in this paper using an electronic circuit analysis program SPICE2, a 16‐valued logic circuit has been shown to be possible with 0.8‐m̈m process even considering the variation in device parameters. As an application of these basic circuits, MIN, MAX circuits, and literal circuit are shown. These circuits have a simple configuration and high speed.
Selective movpe growth and its application to semiconductor photonic integrated circuits
Authors: Sasaki Tatsuya , Yamaguchi Masayuki , Kato Tomoaki , Sakata Yasutaka , Asano Hideki , Kitamura Mitsuhiro , Mito Ikuo 
Published: July 2007

AbstractConsiderable research and development have been done on semiconductor photonic integrated circuits in which various components such as a laser diode and other photonic devices were integrated.In this paper, a 1.55‐μm band wavelength division multiplexing (WDM) integrated light source for optical communication is developed and the results of the evaluation are described. Four‐channel laser sources were fabricated by integrating tunable semiconductor lasers and semiconductor optical modulators plus multiplexers, and the possibility of using a 2.5‐Gbit/s high‐density WDM optical transmission system is discussed.After analyzing the problems encountered in the fabrication of these photonic integrated components, the development of a bandgap energy‐controlling technique of quantum well structure using the selective metal oxide vapor‐phase epitaxial (MOVPE) growth, which is a better fabrication technique, is described. By using this technique, the difficult process of combining the waveguide with a different bandgap energy can be accomplished only by a one‐step crystal growing. This simplifies the components fabrication, and a high‐coupling efficiency of the waveguide between the integrated elements can be obtained.As an application example, the integrated light source was fabricated by integrating a tunable laser, distributed feedback (DFB) laser, and semiconductor optical modulator. Then the tunable characteristic and the extinction characteristic were verified. This simplifies the fabrication method of the previously difficult method of semiconductor photonic integrated circuits and clarifies the possibility of developing a high‐density integrated element.
Oscillation wavelength shift of GaAlAs laser diodes in a magnetic field
Authors: Sato Takashi , Kawashima Hidetoshi , Nakamura Toshio , Ohkawa Masashi , Maruyama Takeo , Shimba Minoru 
Published: July 2007

AbstractThe wavelength shift of laser diodes in a magnetic field has been known for a long time. However, most of the studies have been performed at very low temperatures in a strong magnetic field. An experiment is carried out using laser diodes which oscillate at room temperature and found that the wavelength shift changed significantly, being sensitive to an inner structure. Further, the wavelength shift occurred depending on a magnetic field direction.Previously, the wavelength shift was explained on the basis of the Landau level at very low temperatures in a strong magnetic field. However, such Landau levels are not formed in a relatively weak magnetic field at room temperature; and, thus, the present result cannot be accounted for by the existing theories.This paper describes the experimental results of various types of GaAlAs laser diodes and discusses the mechanism of the wavelength shift and the wavelength control.
Locking Characteristics of Intermodal Injection locking for a Semiconductor Laser
Authors: Iida Yukio , Miyajima Takeshi , Morita Masanobu 
Published: July 2007

AbstractA theoretical and experimental investigation is presented of injection locking on a semiconductor laser by coupling into nonlasing Fabry‐Perot modes.The very interesting behavior of intermodal injection locking is shown by the investigation of detailed locking characteristics. The analysis adopts a formulation similar to that of Lang in the injected mode, and the free‐running mode is expressed by the rate equation for the photon density.The theoretical analysis takes into account the dependence of the refractive index and of the peak gain wavelength on the carrier density and the spectral dependence of the gain function.The experimental results can be explained well qualitatively by the theoretical results. The locking range is located approximately around the center of detuning for the injection locking to a nonlasing mode as far as 18 mode spacings away from the free‐running mode. At the same time, the locking range is shifted toward the lower‐frequency side of detuning and has a symmetric tuning characteristic for that of several mode spacings as in the ordinary injection locking. The former is very useful in application.
A Femtosecond Erbium‐Doped Fiber Laser with a Nonlinear Amplifying Loop Mirror Pumped by Laser Diodes and with Repetition Rate Control of Its Output Pulses
Authors: Yoshida Eiji , Kimura Yasuo , Nakazawa Masataka 
Published: July 2007

AbstractAn erbium‐doped fiber laser with a nonlinear amplifying loop mirror pumped by 1.48‐μm laser diodes was fabricated. A 290‐femtosecond (fs) short pulse was obtained successfully from this laser. The oscillation wavelength was 1.56 μm and the output peak power was as high as 16 W when the pump power was 20 mW. The oscillation threshold was about 50 mW.However, once the laser started oscillation, it continued to oscillate even when the pump power was 10 mW. The repetition rate of the output pulses changed randomly from 5 MHz (fundamental repetition rate) to 2 GHz and could not be controlled. However, using a subring cavity with a length which is 1/n that of the main cavity (n is an integer), a constant pulse repetition rate of 125 MHz was obtained.
Optical mode conversion by magnetostatic surface waves in multilayered waveguides
Authors: Hasegawa Kazuo , Miyazaki Yasumitsu 
Published: July 2007

AbstractConventional optical functional elements which utilize the magnetooptical effect induced by magnetostatic surface waves have been those of a thick film structure for a waveguide to excite a magnetostatic surface wave. Therefore, they can offer a single‐mode waveguide, leading therefore to a degradation of performance due to a coupling between higher‐order modes in the waveguide. Such a waveguide which can propagate only a single fundamental mode without lowering the interaction cross section can be fabricated by constructing a magnetic double‐layer film with two different refractive indices.This paper considers the case where the magnetostatic potential of the magnetostatic surface wave varies significantly near the surface. This structure provides further improvement in mode conversion efficiency and characteristics by adjusting the saturation magnetization of the film. A model for elements is proposed by which one can shorten an interaction length, and the calculated results are discussed.
A Thin‐Film Waveguide Polarizer with SiN Clad
Authors: Kato Isamu , Mori Kazutomi , Sato Koki 
Published: July 2007

AbstractA discussion on a complex refractive index (n = nc″ ‐ jnc″) for a clad film of a thin‐film waveguide polarizer is presented. A guided light of a wavelength 0.5145 μm is chosen. Based on simulation result using a slab approximation, experimental results are discussed for SiN clad films. SiN films are fabricated onto a three‐dimensional waveguide as clad films with a waveguide width 20 μm. Five SiN films with different nc″ (= 0.02, 0.07, 0.12, 0.16, 0.23) are examined for the performance characteristics. As a result, nc″ = 0.16 is found to be best for a TE mode transmission polarizer with an extinction ratio 27 dB and an insertion loss 6 dB. Also, for a TM mode transmission polarizer, nc″ = 0.07 is found to be most suitable where an extinction ratio is 26 dB and an insertion loss is 2 dB.
Stabilization of Voltage Limiter Circuit for High‐Density DRAMs Using Miller Compensation
Authors: Tanaka Hitoshi , Aoki Masakazu , Etoh Jun , Horiguchi Masashi , Itoh Kiyoo , Kajigaya Kazuhiko , Matsumoto Tetsurou 
Published: July 2007

AbstractThe feasibility is examined of using the Miller phase‐compensation circuit to ensure the stability of the voltage limiter circuit in high‐density CMOS DRAMs. First, analytical expressions are obtained for the condition of stabilization to support the comprehensive circuit design and it is shown that both load capacity and load current affect the stability significantly. Second, by using the analytical expressions, parameters for the voltage limiter and the phase compensation circuit are calculated. By computer simulation and experiment voltage variations within the chip are evaluated when the internal circuit operates and external power supply voltage is changed. Results show that the voltage variation caused by the operation of the internal circuit is within 10 percent, resulting in no problem in practice.The voltage variation caused by the change in the external power supply voltage is 3 percent in the case of low‐frequency noise (tr,tf= 1μs) and is as large as 20 percent in the case of high‐frequency noise (tr,tf= 10 ns) and attention must be paid to the latter case in the circuit design.
A Two‐Wire Silicon Capacitive Accelerometer
Authors: Shirai Toshihito , Esashi Masayoshi , Ura Noritake 
Published: July 2007

AbstractDifferential capacitive accelerometers have been fabricated using silicon micromachining, and a capacitance‐detection circuit and hybrid two‐wire sensing system have been realized.The features of the differential capacitive accelerometer are the small influence of both acceleration at other axes and temperature and in restrained parasitic capacitance due to the concentration of efforts on the structural design of the sensor. The sensitivity of the sensor depends on the residual stress in beams supporting the weight.By careful design of the capacitance‐detection circuit, the effect of both power supply voltage and temperature is small while the output signal of the sensor can be obtained from the current flowing in the two wires for power supply.
High‐density recording characteristics of perpendicular magnetic recording with sliding‐contact hard disk system
Authors: Muraoka Hiroaki , Nakamura Yoshihisa 
Published: July 2007

AbstractHigh linear recording density by combining a single‐pole magnetic head and Co‐Cr/Ni‐Fe double‐layer medium in a perpendicular magnetic recording hard disk drive is discussed. The present perpendicular magnetic recording system adopts a sliding contact head‐disk interface suitable for high‐density recording. A spacing as small as 30 nm between a head and a medium is obtained, measured by an optical interference method. Attaining such a small spacing promises superiority of the sliding contact head.An attempt is made to fabricate a composite head (= separate configuration of read/write head) to realize high resolution. This composite head is designed to maintain an important feature of saturation recording in the perpendicular magnetic recording scheme.A computer simulation analysis of the head‐disk interaction shows that a stronger interaction gives rise to a better resolution for a single‐pole head. In view of those results, heads and media with various Co‐Cr thicknesses are fabricated. A high D50 value of 170 kFRPI and a good overwrite performance better than ‐30 dB are demonstrated.
An optical neural network using a feature‐extracting optical neuron device
Authors: Kuratomi Yasunori , Takimoto Akio , Akiyama Koji , Ogawa Hisahito 
Published: July 2007

AbstractA method for feature extraction and an optical neural network model which can easily be implemented in optics have been proposed. In the method, the vector feature which denotes direction, existing position, and length of the line segments included in the pattern is extracted without any negative synaptic weights. It has been shown analytically that the vector feature is superior to the conventional mesh feature for handwritten character recognition.The model using the method is featured as follows: (1) high recognition ability to recognize handwritten characters by extracting vector feature; (2) fast learning convergence; and (3) possibility of all‐optical implementation. By applying a newly developed feature‐extracting optical neuron device to the model, an optical neural network for handwritten character recognition has been constructed. It has also been confirmed that the feature‐extracting optical neuron device can extract four kinds of line segment in parallel processing. Due to the optical parallelism, the device is substantially useful for implementation of massive systems.
Fabrication of stretched gold island films with large optical anisotropy
Authors: Katsu Jun‐Ichiro , Baba Kazutaka , Miyagi Mitsunobu 
Published: July 2007

AbstractAs materials for a polarizer with a large aperture and short length, stretched gold island films with large optical anisotropy have been fabricated and their optical properties have been investigated experimentally. By embedding an island film into a glass medium and stretching the embedded film with large tension, large optical anisotropy can be achieved. When a 90‐Å thick gold island film deposited on a soda‐glass substrate and embedded in a 0.35‐μm thick pyrex glass was stretched five times with a tension of 0.23 kg/mm2 at 650°C, the resonance wavelength of the film changed from 0.54 to 0.95 μm in light polarized in the stretching direction.In light polarized in the direction perpendicular to the stretching direction, the resonance wavelength showed almost no change and was 0.53 μm. The multilayer consisting of the anisotropic island films can be used for a thin optical polarizer with a large aperture.