bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical fiber loss reduction
Authors: Ohashi Masaharu , Tateda Mitsuhiro , Shiraki Kazuyuki , Tajima Katsusuke , Tsujikawa Kyozo 
Published: July 2007

AbstractWith the introduction of optical fiber amplifiers, numerous experiments on long‐haul and large‐capacity transmissions at 1.55‐μm band have been done. To realize high‐grade transmission systems, further reduction of optical fiber losses is necessary.In reduction of optical fiber losses, Rayleigh scattering loss, infrared absorption loss, and losses due to imperfections should be further reduced. Among these, Rayleigh scattering and infrared absorption losses are fixed by the used dopants. On the other hand, losses due to imperfections depend not only on the fabrication process but also on the viscosity properties of the core and cladding materials. To reduce loss due to imperfections, the viscosity matching of core and cladding materials is quite effective. This type of viscosity‐matching technique, unexplored until now, will be clarified by the authors.The method of viscosity matching over the fiber cross section is first presented; then the viscosity characteristics of silica glasses doped with GeO2, F, or codoped with GeO2 and F together with their Rayleigh scattering behavior are experimentally clarified. Finally, the loss behavior of fabricated viscosity‐matched fibers is described and the effectiveness of the matching technique is demonstrated.
Stress‐applied polarization‐maintaining optical fibers. Design and fabrication
Authors: Hosaka Toshihito , Sasaki Yutaka , Okamoto Katsunari , Noda Juichi 
Published: July 2007

AbstractTo realize low‐loss low‐crosstalk long‐length polarization‐maintaining fibers, this paper examines the “PANDA fibers” having a circular stress‐applying part which has a high design accuracy and ease of fabrication. Stress‐applied type polarization‐maintaining optical fibers generally have two orthogonal polarized modes, and their coupling causes crosstalk which makes the transmission of polarized mode through a long‐length of fibers difficult. To suppress this mode‐coupling, it is important (a) to make the modal birefringence larger, and (b) to reduce the deterioration of the symmetry of the stress applied. This paper examines the circular stress‐applying type PANDA fiber and compares it with two other types of PANDA fiber having the typical shapes of the stress‐applying part. As a result, (1) the structure parameters of the stress‐applying part which gives the maximum modal birefringence and a low loss, and (2) the mode‐coupling parameter, with the stress‐applying part deviated, which can evaluate the crosstalk characteristics, have been obtained. Based on the results of these theoretical analyses, the symmetry in the stress‐applying part is improved by using a large preform, and the increase of the modal birefringence by increasing the outer diameter of the fiber is carried out. The circular stress‐applying type PANDA fiber having a crosstalk as low as ‐42 dB in 1 km has been realized.
Remanent polarization of vacuum‐deposited BaTiO3 films
Authors: Iijima Yoshio 
Published: July 2007

AbstractHysteresis curves exhibited by vacuum‐deposited BaTiO3 films are studied. Platinum substrates and temperatures from 600 to 900°C were employed. The hysteresis curves did not vary greatly in height despite frequency variations. This was due to the generation of terminal voltages on the integrating capacitor as a result of remanent polarization of the samples. The measured value of the remanent polarization exceeded 10 μC/cm2 (E = 5.3 kV/cm).
Bipolar transistor CAD model including quasi‐saturation phenomena
Authors: Shinmi T. , Inohira S. , Nagata M. , Iida K. , Nakagome Y. 
Published: July 2007

AbstractIn the Ebers‐Moll type model excluding quasi‐saturation phenomena and the Van der Ziel model neglecting the base electrical conductivity modulation effect, simulation of integrated circuits was insufficient due to the degrading accuracy of hFE and the fT fall‐off at high currents and collector voltage dependency. This paper proposes a new model introducing the conductivity modulation of the base region (Kirk effect) and the critical current ICRI with a simple formulation. To put the new model into a circuit analysis program of the nodal analysis, a linearization method using an equivalent linear current source is demonstrated. Circuit simulation of a linear IC for a Hi‐Fi stereo preamplifier is performed using the circuit analysis program into which the new model is programmed and a very good agreement is obtained with the experimental results. Hence, it is confirmed that the accuracy of fFE and fT at high currents is improved. Also, simulation accuracy even in an operating region in which quasi‐saturation for the IC level occurs, is improved.
Measurement of electrical field distribution around a biological body by an optical technique
Authors: Endo Hideto , Shimizu Koichi , Matsumoto Goro 
Published: July 2007

AbstractWhen a biological body enters a uniform unperturbed field, the field is distorted by the body and the field concentration occurs on various parts of the body. To elucidate the biological effects of strong electric field, the coupling of the electric field to a biological body has to be well understood and the field exposure dose to a biological body has to be evaluated qualitatively. Using an optical field sensor with a minimum field perturbation, we have developed a system which can visualize the spatial distribution of the field around an object with a complex shape such as a biological body. First, the accuracy of the measurement was confirmed through comparison between the measurement and theoretical calculation using the model with a simple geometry. Second, the field distributions were measured with experimental animals and it was shown that a conductor model can be used instead of a living body in this frequency range. Based on these results, the field distributions were measured with a human model in various conditions found in common everyday life. These results will provide useful information on the behavior of the field around a human body.
Formation and properties of vacuum‐evaporated high conductivity n‐type CdTe film
Authors: Kawai Yoshiji , Ema Yoshinori , Hayashi Toshiya 
Published: July 2007

AbstractHigh dark conductivity CdTe films have been prepared by a co‐evaporated process of CdTe and Cd. The structural, electrical and optical properties were investigated. Dark conductivity of the film increased monotonically with an increase of the co‐evaporated Cd. The highest dark conductivity of the film obtained in this experiment was 0.54 ohm‐1 cm‐1. The film structure was of the zinc‐blend type with a preferential orientation of the (111) planes parallel to the substrate and fibers. The crystallinity of the dark films was similar to films without Cd doping. This high dark conductivity film will be useful for thin film CdTe solar cells.
Magneto‐optic readout of magnetically recorded signals using magnetic garnet film
Authors: Nomura Tatsuo , Tokumaru Haruki 
Published: July 2007

AbstractExperiments have been carried out to obtain a method different from the conventional method, to optically read out the signal recorded on a magnetic recording medium by transferring it to a magnetic garnet film. This method forms straight parallel stripe magnetic domains in the garnet film, and the read‐out is done by varying the domain width using the stray field from the recording medium.Static transfer and dynamic readout experiments have been done using a garnet film with straight stripe magnetic domains with the domain width of 2.25 μm and the domain period of 4.5 μm. Statically, the transfer of the signal with a wide range of recording wavelength 5 μm‐200 μm was done without any domain disturbances. Also, there were no unnecessary domains between the transferred tracks. On the other hand, when the magnetic sheet disk was rotated with a relative speed of 50 m/s, a stable readout of the signal with 0.25 MHz to 10 MHz was possible using a laser beam with a spot radius of 5 μm.These experimental results indicate that the new transfer method is suitable for a signal read‐out of narrow track recording, and that it is superior in high‐speed response. Further, from the analysis of the readout model, a further improvement of the readout characteristics is shown possible by reducing the spot radius.
Finite‐element analysis of planar anisotropic inhomogeneous optical waveguides
Authors: Kumagami Hiroshi , Koshiba Masanori , Suzuki Michio 
Published: July 2007

AbstractDiffused optical waveguides are of considerable interest for the construction of optical integrated circuits. Generally, it is difficult to analyze inhomogeneous waveguides, such as diffused waveguides, because their refractive indices change continuously. Further, it is complicated and difficult to analyze anisotropic inhomogeneous lossy optical waveguides. This paper describes the finite‐element method for the analysis of planar anisotropic inhomogeneous lossy optical waveguides. The validity of the method is confirmed by comparing numerical results of planar isotropic inhomogeneous optical waveguides with exact results. The numerical results of metal‐clad planar anisotropic inhomogeneous optical waveguides are also presented and the effects of metal claddings on the propagation characteristics for the surface waves and the leaky surface waves are examined.
Effects of smoothing condenser on the stability of the push‐pull current‐fed dc‐dc converter
Authors: Harada Koosuke , Kim Heejun 
Published: July 2007

AbstractThe push‐pull current‐fed dc‐dc converter has been considered as one of the circuit configurations for the dc‐dc converter. According to past studies, this converter is useful from the viewpoint of the voltage stability compared to traditional circuits. This paper considers the fact that the capacitance of the smoothing condenser can be reduced by raising the switching frequency. The relation is determined between the voltage stability and the capacitance of the smoothing condenser by analysis, considering the phase‐delay element in the feedback circuit and the equivalent series resistance of the smoothing condenser. Hence, the push‐pull current‐fed dc‐dc converter is shown to have better voltage stability than the traditional buck‐type converter, even if the capacitance of the smoothing condenser is reduced, while the output voltage ripple increases with the increase of the output current, thereby limiting practical applications.
A simplified model for the diffusion and collection of alpha‐particle‐induced carriers
Authors: Kawakami Akira 
Published: July 2007

AbstractAs LSI technology advances, the evaluation of noise charge due to α‐particle or the like has become more important in the total design. In the case of RAMs, in particular, the amount of charge collected by circuit nodes can easily be approximated by the solution to the heat conduction differential equation for the diffusion charge component, and assuming that all of the charge in the depletion region is collected. Using the diffusion equation point source solution with the method of images to satisfy the boundary conditions, a simplified analytic expression can be obtained. However, since a more realistic noise source is usually a finite line, a Fourier expansion approximation extending the initial source along the coordinates directions is useful. In an infinite medium, introducing an absorbing boundary sufficiently removed from the collecting region still remains a Dirichlet problem. The analytic expressions developed as a result of these considerations are applicable to arbitrary incidence and are suitable for computer treatment. They allow estimates to be made easily for such things as the effect of buried protection layers or the influence of device isolation structures, etc.
GaAs broadband monolithic switches
Authors: Yamao Yasushi , Sugeta Takayuki 
Published: July 2007

AbstractA high‐frequency switch utilizing a GaAs FET as an analog switch is expected to operate in a broad band and can be integrated in a monolithic IC form. Since only a single power supply is needed for the gate bias and the power consumption of the switch can be made zero, it is useful in the area where a small size and low power consumption are required. To investigate the feasibility of a broadband GaAs monolithic switch, this paper first derives an equivalent circuit of the switch from the structural model of the FET and the relation between the switch characteristics and the device parameters of the FET. The design method of the switch is then developed. Next, the monolithic switches of SPDT and DPDT structures are fabricated by ion‐implantation technology and their characteristics are evaluated so that the validity of the equivalent circuit model is confirmed. The GaAs monolithic SPDT switch realized has the passband of dc to 3.3 GHz, insertion loss less than 0.7 dB (dc to 2 GHz), isolation more than 20 dB, switching time 2 ns and the maximum distortionless signal input power 20 dBm. Similarly, good performance has been obtained for the DPDT switch.
Measuring system for ionic channel noise of the biological membrane current—application to the exocrine gland acinar cells
Authors: Izumi Takashi , Hoshimiya Nozomu , Kazami Kunio , Matsuo Tadayuki , Nishiyama Akinori 
Published: July 2007

AbstractIonic channels in biological membranes are one of the elementary transport elements passing specific ions across the membranes. The objective of this investigation is to design a two‐microelectrode‐voltage clamp system which is able to detect ionic channel noise of the membrane current in the mammalian exocrine gland acinus, an electrical unit, consisting of about 100 acinar cells. Since two high‐resistance intracellular microelectrodes are used, the coupling capacitance between two electrodes makes the operation of the measurement system unstable and places a severe restriction on the experiment. In our measurement system a simple low‐pass filter is inserted in the feedback system of the membrane voltage. As a result, the system operation is stabilized via the compensation of the frequency characteristic of the feedback system. If the noise inherent to the measurement system is large enough to mask the ionic channel noise of the membrane current, the channel noise below the noise level of the system cannot be detected. Since the noise of the measurement system is found to be due mainly to microelectrodes, properties of the electrode noise are analyzed in the present work. From the results, the system noise is evaluated quantitatively and the detection limit of the ionic channel noise is determined. Furthermore, the voltage is clamped for the electrically equivalent circuit to the acinar surface membrane and the operation of the voltage clamp system and the system noise level are investigated experimentally.
Short‐term frequency stability of crystal oscillator circuits with the current noise in transistor
Authors: Sakuta Yukinori , Sekine Yoshifumi , Suyamas Masatoshi 
Published: July 2007

AbstractWith the widespread and detailed applications of the frequency bands, it is desired especially to improve the short‐term frequency stability of the highly stable crystal oscillator. It is necessary to investigate not only the crystal element, but also the oscillator circuit. In the past, the amplifier has primarily been investigated theoretically from the viewpoint of frequency stability, and studies on the oscillator have been insufficient. This paper investigates the effect of the current noise of the transistor in the crystal oscillator on the short‐term frequency stability. By converting the current noise of the transistor equivalently to the change of the dc operating point, the change in the load capacitance of the oscillator circuit is evaluated. Then the short‐term frequency stability is valued, revealing that it is determined largely in the crystal oscillator by the current noise of the transistor. By the analysis based on Ebers‐Moll's model, it is verified that the analysis describes clearly the operational characteristics of the oscillator, taking into account the nonlinear property of the transistor. It is also shown that the change of the oscillation frequency by the change of the dc biasing point of the transistor is due to the change of the load capacitance.
Accuracy of optical path lengths computed with an asymptotic solution for a meridional ray equation in GRIN‐rod lenses
Authors: Sakamoto Toyokazu 
Published: July 2007

AbstractThe accuracy is studied of the optical path lengths computed with an asymptotic solution of a meridional ray equation in GRIN‐rod lenses derived by Streifer and Paxton [4]. Assuming the sech index profile, it is shown that the accuracies of normalized optical path lengths computed with second‐, third‐ and higher‐order asymptotic solutions are, respectively, O(10−5) and over (10−6) within N.A./n0 = 0.3, where N.A. and n0 denote the numerical aperture and the refractive index on the center axis, respectively. It is shown also that within N.A./n0 = 0.2, an accuracy of O(10−6) can be obtained using the second‐order asymptotic solution.
High‐performance optical switch using thermo‐optic effect
Authors: Hashimoto Ken‐Ya , Nakamura Yutaka , Yamaguchi Masatsune , Kogo Hiroshi 
Published: July 2007

AbstractThe TO switch, in which the temperature dependence of the refractive index is used, is considered to have a potential for replacing a purely mechanical version as a switching device for optical channel selection. This paper studies theoretically and experimentally TO switches for improving their performance. First, for a simple model of a TO switch, the switching speed and deflection angle are obtained theoretically. Fundamental experiments have been performed for these characteristics so that the validity of the theory is confirmed. It is found that the switching speed and deflection angle depend not only on the fundamental material constants, but also on the shape of the heating parallel electrodes has been proposed in which the optical beam is extracted by reflection inside the switch substrate. A switch based on this principle has been fabricated. With switching speed less than 0.4 ms and a driving power of 1 W, the deflection angle is more than 1.7 deg. The results confirm the effectiveness of the proposed structure.
Effect of humidity on electrical properties of thin‐film Li‐Te junction
Authors: Kitagawa Hiraku 
Published: July 2007

AbstractRelative humidity (H) ‐ current (I) characteristics were investigated on test samples of thin‐film Li‐Te junction humidity sensing devices. (Fabricated by vacuum deposition and then thermally treated for 60 min at 100°C.) The devices had 15‐V ac applied, and the H ‐ I characteristics were measured for relative humidities between 30 and 90 percentThe H ‐ I characteristic curves had minima at 80 percent R.H., and were linear from 30 to 70 percent. The devices differ from conventional humistor resistive humidity sensors in that the H ‐ I characteristics has decreasing current at high R.H., decreases. This unique characteristic can be exploited for a sensor well suited to low R.H. measurements. The response time is 4 to 20 s depending on the initial R.H. and the humidity change. The H ‐ I characteristic also shows good reproducibility for relative humidities between 30 and 70 percent. Auger depth profile analysis revealed that the Li‐Te junction device is formed of an Li2O + Te surface layer, and an inner layer Li2O layer, with a boundary junction between them.
1/f noise in ion‐implanted GaAs
Authors: Hashiguchi Sumihisa , Sugiyama Hisashi 
Published: July 2007

AbstractThe 1/f noise is believed to be caused by the lattice scattering in the bulk, and also that the noise is proportional to (μ/μL)2, the square of the ratio of the total mobility μ to the lattice scattering mobility μL. In this paper, the mobility has been changed by varying temperature, and the relation between the noise and the mobility has been studiedIn the measurements with a GaAs Hall device, we have observed that the 1/f noise is proportional to (μ/μL)2 at low temperature, but that an effect of the temperature change on the magnitude of the 1/f noise appears strongly around the room temperature. In the present measurements we used GaAs MeS samples in order to control the effect of the surface current on the noise performance. In the samples with a low gate‐leakage current, the 1/f noise was proportional to (μ/μL)2 at 77 K ˜ 300 K. In the sample with a high gate‐leakage current, a strong temperature dependence, which coincides with that of the gate‐leakage current, was observed in the 1/f noise. Thus, it is concluded that there is a strong effect of the surface current on 1/f noise.
Computer analysis of crystal oscillator
Authors: Adachi Takehiko , Tsuzuki Yasuo , Hirose Motoyoshi 
Published: July 2007

AbstractIt has been considered almost impossible to analyze the characteristics of a crystal oscillator circuit on the operating signal level. Such oscillator usually consists of a capacitive active circuit with a negative resistance connected to a crystal resonator. If the crystal oscillator circuit is divided into the resonator and the active circuit at the terminal of the crystal resonator and the characteristic of the active circuit is independently obtained, the oscillation characteristics can be found for connection of an arbitrary resonator. Based on this concept, a method for analysis of the characteristics of the crystal oscillator is introduced in this paper by means of a general purpose circuit analysis program. The analysis is conducted for an adjustment‐free Colpitts crystal oscillator used in practice in the frequency range of 10∼30 MHz. The results are compared with the measured data. The negative resistance, equivalent capacitance and the resonator current of the circuit are analyzed and the results are seen to be in good agreement with the measured data. The source voltage dependence of the oscillation frequency, which is important in design, is investigated. The frequency variation of the ppm order is analyzed and agreement with the measured data is excellent. The method in this paper is believed useful for improvement of oscillator design.
Prototype of micro ISFET for biomedical research
Authors: Shoji Shuichi , Esashi Masayoshi , Matsuo Tadayuki 
Published: July 2007

AbstractWith a view to developing an ion sensor capable of simple measurement of ion concentration at the cell level, a micro ionsensitive FET (micro ISFET) has been studied. For this purpose, it is necessary that the micro ISFET be a probe structure whose tip size is smaller than the cell and that the ion‐sensitive gate be placed at the tip of the probe. Special micro fabrication techniques are required for such a micro ISFET. This paper describes a three‐dimensional processing technique to fabricate a microprobe from an Si wafer and a method for forming an ISFET on a Si probe. Based on these fabrication techniques, a fundamental design of the micro ISFET is performed. An Si3N4 gate micro ISFET for pH is fabricated that has a tip size of 10 μm and a gate area of 5 × 5 μm2. Its characteristics are evaluated.