bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coupling characteristics of nonparallel dielectric waveguides
Authors: Tomabechi Yoshiro , Matsumura Kazuhito 
Published: July 2007

AbstractA coupled mode equation for two nonparallel dielectric waveguides is rigorously derived from the Lorentz reciprocity theorem. the waveguides are located close to each other. Two local coordinate systems are introduced to present an intrinsic mode function. A global coordinator system also is employed to solve the coupled mode equation. As a numerical example, a coupling system consisting of two dielectric disks with different radii is analyzed. the coupled mode equation for whispering gallery modes propagating along a circumference of the disks is solved numerically in the global coordinate system. Eigenvalues of the whispering gallery modes are complex numbers because of radiation and dielectric losses. As a result, electric field distribution and the coupling coefficient around the coupling system are obtained quantitatively.
A method of calculating step‐shape characteristic in a rectangular waveguide using a transmission equation
Authors: Suga Takashi , Ishihara Fujio 
Published: July 2007

AbstractIt is demonstrated that the step shapes in a rectangular waveguide can be treated rigorously by a transmission equation. an efficient method for computing the characteristics of the step shapes is proposed based on the transmission equation. It is recognized that the step shape is the one in which the derivatives of the shape change in the axial direction diverges. Then the transmission equation is simplified. It is shown that the frequency dependence can be eliminated from the transmission equation if there is no thermal loss in the step shape and that the scale dependence can also be eliminated if the cross‐sectional shape is similar.By the foregoing procedure, the computation time and the number of computation of the F matrix which consumes the most time in the transmission equation method can now be reduced substantially. It is found that the computation speed can be accelerated effectively by more than one order of magnitude in comparison to the method in which the F matrix is computed by numerical integration. the results are verified experimentally.
Characteristics of ta2O5 thin film prepared by electron beam heating method
Authors: Sekido Yoshihiro 
Published: July 2007

AbstractA Ta2O5 film formed by ϵ‐beam evaporation (EB‐Ta2O5) was nonstoichiometric because of oxygen deficiency, resulting in electron trapping. As a result, the dielectric constant was higher than that of bulk material. the trapped fixed‐charge density increased with a decrease of film thickness.When the film was 300 nm, the trapped fixed Charge density was as high as 1016 cm−3. However, when the film was thicker than 300 nm, it decreased rapidly. the dielectric constant approached the bulk value as the film thickness increased, and the film resistance was low because of oxygen deficiency. When the film was 300 nm, the resistivity p was 107 − 108 ω ‐cm (5 × 105 V/cm). When the electric field reached about 7 × 105 V/cm, only the current density increased in spite of the slight increase of the electrical field.When the film was thicker than 300 nm, the resis tivity increased and the clamp field became unclear with an increase of thickness. an EL (electroluminescent) device was formed using the EB‐Ta2O5 film sandwiched with SiO2 films as the luminescent film. the luminance of the device was 100 cd/2. the luminescence spectrum had peaks at 380, 430, 475, and 540 nm, indicating that there were energy levels at 3.2, 2.9, 2.6, and 2.3 eV.
Conditions of palladium oxide formation caused by mechanochemical reaction
Authors: Yamamoto Takeshi , Sawa Koichiro 
Published: July 2007

AbstractPalladium has a strong anticorrosion characteristic and has been used as low‐load contact material. This paper investigates the mechanochemical reaction of palladium, which is believed to cause contact failure due to palladium oxide. As a result, it is found that the formation of palladium oxide did not occur when pressure is lower than a certain value and that critical pressure decreases with a decrease of moisture.It also is found that water vapor suppresses the formation of palladium oxide due to the mechanochemical reaction. It is proposed that the oxidation of palladium is suppressed by the lubrication effect of water vapor. In addition, experiments are carried out under the ambient without water vapor and organic gas; and it is found that the proposition was valid.
Magnetic field modulation recording with multipulse laser irradiation on magnetooptical disk drive
Authors: Kawasaki Satoshi , Sohmuta Mitoshi 
Published: July 2007

AbstractA magnetooptical disk driver which adopts the magnetic field modulation recording scheme has been developed for filing data. to apply the magnetic field modulation magnetooptical file system, such as a minidisk, to personal computers, essential technology must be developed. A noncontact magnetic head type and active spacing system were adopted to achieve high reliability and accessibility.To avoid system disturbance due to the weight increase in the head, linear motors were used to achieve independent motion of the optical head and magnetic head. A sputter‐etching treated magnetooptical disk was developed as the magnetic field modulation medium for low‐field recording. to cope with low‐field noise during magnetic field modulation recording, multipulse laser irradiation was used. In this method, the magnetized segment had a sharp edge even when the magnetic field was weak, resulting in a reduction of jitter in the playback of the signal.Using the foregoing technologies, a test driver for recording and playback using the compact disk (CD) format was evaluated. In the test, the jitter value was less than 20 ns and the block error rate was on the order of 10−4.
Four‐wavelength DBR laser array using selective MOCVD growth
Authors: Katoh Yukio , Kunii Tatsuo , Matsui Yasuhiro , Wada Hiroshi , Kamijoh Takeshi , Kawai Yoshio 
Published: July 2007

AbstractA four‐wavelength DBR laser array, fabricated using selective metalorganic vapor‐phase epitaxy (MOCVD) growth, has been developed as a light source for a wavelength division multiplexing (WDM) system. Four different lasing wavelengths were obtained by varying the thickness of the waveguide. This enabled fabrication of lasers having different wavelengths but gratings with the same pitch.First, the InGaAsP layer grown on an InP substrate which was patterned with stripes of different widths by using an SiO2 mask is evaluated. the growth rate of the InGaAsP layer between SiO2 masks could be varied to twice as fast as in a flat area while maintaining good quality of the crystal. Next, a four‐wavelength DBR laser array is fabricated by using selective MOCVD growth and a grating with the same pitch. the lasing wavelength was controlled at 5‐nm intervals over a 15‐nm range.
Design of very low‐distortion, four‐quadrant analog multiplier‐type CMOS‐OTA considering variation of mobility according to the gate voltage
Authors: Igarashi Yutaka , Hyogo Akira , Sekine Keitaro 
Published: July 2007

AbstractThis paper discusses the four‐quadrant multiplier‐type operational transconductance amplifier (FQAMTOTA). the basic principle of its operation is described. the circuit uses four MOSFETs (MRA) operating in the resistor region as well as the identical voltage level‐shift circuit (IVLS). Although it has a simple structure, its feature is that it has a wide linear input range and the transconductance can be controlled for both signs. For the FQAMT‐OTA to operate at a high‐frequency signal range, MOSFET with a short channel must be used as MRA.In most of the past designs of CMOS circuits, the effective carrier mobility μ is assumed as constant. In practice, however, μ has the property that it depends on the gate‐source voltage. This effect cannot be ignored when the circuit is designed using MOSFET with a short channel because it can cause a large second‐order harmonic distortion in the output of FQAMT‐OTA. Another point is that the power consumption increases when MOSFET with a short channel is used. the idea in this paper is that those problems can be remedied only by using the bootstrap circuit as MRA. A construction of the improved FQAMT‐OTA is shown together with the result of simulation using PSpice.
Integrated master slice‐type transimpedance amplifier photosensors using pin‐bipolar process
Authors: Kyomasu Mikio 
Published: July 2007

AbstractMaster slice‐type transimpedance (TZ) amplifier sensors based on the pin‐bipolar process are developed which have applications in optical communications, computer LAN, rangefinding apparatus, and optoelectric switches (optoelectronic SW). the pin‐bipolar process is used in these devices and the pin photodiodes, together with the detector current amplification circuitry, are monolithically integrated by master slicing on the substrate. It became possible to alter the photodiode area of octagon of 0.5 mmϕ, that of 0.8 mmϕ, or □ of 1.0 mm2by changing only the aluminum interconnections. Further, the photodiodes are separated by dielectric isolation andp+diffusion, which enabled the achievement of low crosstalk and successful design of receivers matched to the characteristics of the TZ amplifier. In the integrated circuit area, the wideband amplifier, the inverter, and the wideband differential amplifier are included, to which the specific capacitance prepared by the pin‐bipolar process is added. These allowed design of master slice‐type integrated optical sensors by changing only the aluminum interconnections and contact mask of each TZ amplifier. the chip size of the achieved device, sealed in the TO‐18 package suitable for uses as integrated TZ amplifier sensors, is 1.7 × 1.7 mm2□.From the evaluation results of the designed device, the cutoff/frequency was found to be about 150 MHz with the minimum sensitivity of 1.3 mV/nW and allowable external light intensity of 30μW. These results show that the master sliced TZ amplifier can satisfactorily respond as an integrated optical sensor.In other applications, it is indispensable to overcome the problem of master slice realization of arbitrary shape photodiodes. In this respect, the isolation technique developed here is believed to be an attempt in their realization.
Cl2‐ECR plasma etching of III/V semiconductors and its application to photonic devices
Authors: Yoshikawa Takashi , Kohmoto Shigeru , Sugimoto Yoshimasa , Asakawa Kiyoshi 
Published: July 2007

AbstractA 1.3‐μm InGaAsP/InP laser diode (LD), a 1‐μm InGaAs/GaAs LD, and a 0.65‐μm GaInP/AlGaInP LD were fabricated using Cl2 reactive ion beam etching. Four desirable features of dry etching, i.e., smoothness, controllability, uniformity, and capability of fine pattern formation, were investigated through the fabrication of these devices. the morphology of dry‐etched InP generally is not as good as that of GaAs; but, nevertheless, we achieved very smooth InP etching with a roughness of only 1.4 nm. the InGaAsP/InP LD made using this etching had a threshold current of 20 mA, which is as low as that of a wet‐etched LD. Precise control of etching depth is necessary for AlGaInP‐LD fabrication, and ion‐current monitoring made this possible with an accuracy of 22 nm. the deviation of AlGaInP etching depth is only 15 nm across a 2‐inch wafer. This good uniformity resulted in a small deviation of threshold current fabricated in 2‐inch form. an InGaAs/GaAs vertical‐cavity surface‐emitting laser array having uniform threshold current was fabricated making use of the capability of fine pattern formation, and the record low‐threshold current of 190 μA was achieved in an air‐post VCSEL etched by reactive ion beam etching (RIBE).
Dynamic characteristics of the voltage‐resonant converter controlled by multiple resonant switches
Authors: Sato Terukazu , Nakano Tadao 
Published: July 2007

AbstractThe small‐signal ac dynamic characteristics of the voltage‐resonant converter controlled by multiple resonant switches are analyzed, the resistances of the switches and diodes, equivalent series resistances of the resonant inductors and capacitors are taken into account, and numerical calculations utilizing the state transition matrix are applied. Analytical and experimental results are in good agreement, and the effects of parasitic resistances and filter elements on dynamic characteristics are clarified.
Low‐power quadrature modulator ICs for digital mobile communications
Authors: Yamao Yasushi , Saito Shigeki 
Published: July 2007

AbstractLow‐power monolithic quadrature modulators for digital mobile communication have been realized for 800‐MHz and 140‐MHz bands. Considering the application to ultrasmall portable telephones, the design reduces the power consumption drastically and realizes a complete one‐chip configuration with no adjustments or external parts. For this purpose, several proposals are made for the circuit configuration.First, a total configuration using a constant phasedifference‐type 90° combiner is proposed to reduce the circuit size and chip area dramatically and to eliminate the phase adjustments. Next, for a double balance mixer (DBM) which is the key for modulation characteristics, an analog‐switch‐type DBM is used for the 800‐MHz band and realizes a highly accurate modulation wave without the influence of device variation due to the semiconductor fabrication process. Furthermore, a bootstraptype buffer amplifier with high current utilization has been devised for the output stage.The fabricated 800‐MHz band (GaAs) and 140‐MHz band (Si) quadrature modulator integrated circuits (ICs) have shown superior performance as π/4 shift QPSK modulators. the power consumption is 65 mW and 32.5 mW, respectively, realizing a dramatically low power compared to conventional methods.
Volume integral equation for analysis of quantum electron waveguide circuits
Authors: Tanaka Kazuo , Yoshino Yoshikatsu , Ootera Hiroki 
Published: July 2007

AbstractThis paper derives the volume integral equation that becomes a foundation for a CAD for electron waveguide circuits with complicated geometry. the derived integral equation can be used for design of a waveguide circuit in which the potential distribution is inhomogeneous and the potential outside the waveguide is finite. Further, the integral equation can be the foundation of the potential scattering theory for a waveguide (channel) configuration. Since the derived integral equation is structurally almost identical to that of the conventional equation, it can be analyzed numerically using directly the moment method. In the case where the potential outside the waveguide is finite, the characteristics of a simple electron waveguide circuit ware analyzed. the mathematical validity of the volume integral equation and the effectiveness of the analysis method are investigated.
Modeling of anisotropic graded‐index channel waveguides
Authors: Matsumae Kotaro , Koshiba Masanori 
Published: July 2007

AbstractWith a view to make the finite‐element analysis of anisotropic graded‐index channel waveguides efficient, quadratic triangular elements are used. In addition, an application of the numerical integration formula by Hammer et al. is attempted for the integration calculation necessary for formation of the element matrix. Numerical investigation has been carried out for a Ti‐diffused LiNbO3 waveguide. It is confirmed that highly accurate solutions can be obtained with small‐scale computation in the present method.Also, it is found that, if the past is still used, significant defference appears in not only the phase constant of the guided mode but also in the coupling length of the optical directional coupler indispensable for configuration of the optical integrated circuit, compared with the results considering the anisotropy. Further, the validity of the results by the scalar finite element method is confirmed by comparison with the results by the vector finite difference method.
Temperature‐compensated crystal oscillator using a two‐port crystal resonator
Authors: Ueno Yoshifusa 
Published: July 2007

AbstractIn general, the oscillation frequency of a quartz crystal oscillator is shifted by varying the load capacitance of the quartz crystal resonator. Since the relation between load capacitance and oscillation frequency of the crystal resonator is nonlinear, the rate of change of frequency is slightly different from the load capacitance before and after the frequency shift. When the variation of oscillation frequency due to aging is compensated using the temperature‐compensated crystal oscillator (TCXO) or the voltage‐controlled temperature‐compensated crystal oscillator (VCTCXO) or the oscillation frequency is shifted, the frequency compensation amount set by the temperature compensation circuit is different before and after the compensation. Thus, the frequency versus temperature characteristics vary.To solve this problem, the author has developed a special quartz crystal resonator with two‐port electrodes. Since this crystal resonator has two load capacitances, the compensation of the temperature characteristics and the shift of oscillation frequency can be conducted independently. Thus, the problem of the changes in the temperature characteristics due to the oscillation frequency shift of a TCXO has been solved. This problem could not be solved using the conventional quartz crystal oscillator having only one capacitance.In this paper, measurement is made under the condition that the oscillation frequency of the TCXO using a two‐port crystal resonator is shifted by ± 15 ppm and the performance is compared with that of TCXO using a conventional crystal resonator. the measurement has revealed that the change of frequency versus temperature characteristics is extremely small when the oscillation frequency of the TCXO using a two‐port crystal resonator is shifted.
Alteration of the electrical properties of anodized silicon/crystal silicon sample by water vapor
Authors: Motohashi Akira 
Published: July 2007

AbstractWhen the ambient surrounding an anodized silicon device changes from vacuum to polar gas, the static capacitance C increases and resistance R decreases. These changes are more than one order of magnitude and are reversible. the electrical property is sensitive to humidity and is characterized by CR = 1/ω (ω is the frequency) or C = const. the fastest response of C was observed during the period when water molecules diffuse to a depth of about 10 μm in the anodized layer. the change of R under low humidity was found to be constant per one water molecule adsorbed on the inner surface in the anodized silicon.
Simulation of single‐electron logic circuits
Authors: Kuwamura Nobuhiro , Taniguchi Kenji , Hamaguchi Chihiro 
Published: July 2007

AbstractUsing the Monte Carlo simulation which can handle the motion of each electron, the transient operation characteristic of a quasi‐CMOS inverter circuit proposed by Tucker [1] was evaluated. It was found that: (1) the output voltage of the inverter circuit depends on the load capacitance, and (2) the propagation delay time can be as short as 10 ps if a tunnel junction with a capacitance of 1 aF is formed. In addition, by evaluating the standard deviation of the inverter output signal, the limit of operating temperature for the integrated circuit was analyzed quantitatively.
Sliding contact characteristics of new composite materials
Authors: Watanabe Yoshitada 
Published: July 2007

AbstractComposite materials of solid lubricants such as graphite, MoS2, WS2, etc., and metals are used as electric sliding contacts. However, few reports on the detailed characteristics of these composite materials have been made so far.In this paper, to satisfy the broad market requirements and, in addition to the Cu‐Nb system reported previously, four newly developed and new commercialized types of Cu‐Sn system materials are investigated. As a result, it was found that the composite material Cu‐Nb system is superior to the Cu‐Sn system and it is clarified that both contact resistance and the coefficient of friction could be made lower in composite materials containing exclusively WS2 and free of MoS2.
Fundamental characteristics for ground‐resistance reducing material using water‐absorbent polymer
Authors: Yamane Hiroshi , Ideguchi Tsuyoshi , Tokuda Masamitsu , Koga Hiroaki 
Published: July 2007

AbstractAs the number of communication facilities increases, the number of grounding points needed for the facilities increases. In the high ground‐resistance areas with soils composed of volcanic ash or sand, it is difficult to achieve the specified ground resistance and, hence, a ground resistance‐reducing material must be used.This paper proposes a method to reduce ground resistance using water‐absorbent material. Also, a method is described for measuring ground resistance using a box‐type metal container, where the influences from the walls and the bottom of the metal container are taken into account.The properties of the ground resistance‐reducing material based on the water‐absorbent material which was solidified by using epoxy resin has been investigated to find the condition where the ground resistance was lower than when a grounding electrode was used and the compressive strength of the material was higher than that of bentonite. As a result, it was found that, when the water‐absorbing ratio was 1:2, the ratio of the weight of the water‐absorbent material to that of epoxy resin should be between 0.3 and 1.7.It was found also that this ground‐reducing material was as effective as a grounding electrode with respect to the buried depth and earth conductivity and that the ground resistance decreased exponentially with a buried radius (αr−0.37).
Design and characterization of traveling wave optical modulators of LiNbO3 thin film waveguides grown by liquid phase epitaxy
Authors: Ohno Kazushige , Kouyama Tatsuya , Tsuji Masahiro , Nakamura Masanori , Izutsu Masayuki 
Published: July 2007

AbstractUsing the liquid phase epitaxial growth (LPE) method, an LiNbO3 thin‐film optical waveguide was formed on LiNbaO3 substrate with MgO added at 5 mol percent. This is channelized by Ar plasma etching so that a ridged waveguide is created. the TM mode optical propagation loss of this waveguide is 1.2 dB/cm at wavelengths of 1.55 μm and 0.83 μm. By means of this waveguide, a Mach‐Zender‐type optical intensity modulator was designed. the operating voltage was compared with that in a modulator designed with a Ti‐diffused LiNbO3 waveguide. It was found that the electrooptic effect was approximately equal. Further, in the optical intensity modulator formed with traveling wave electrodes, the operating voltage was 4.6 V and the optical 3‐dB bandwidth was more than 6.5 GHz in the frequency measurement at a wavelength of 1.55 μm.
LiNbO3 waveguide etalon array for frequency reference
Authors: Sakai Yoshihisa , Miyazawa Hiroshi , Mitomi Osamu , Kaino Toshikuni 
Published: July 2007

AbstractThis paper investigates the LiNbO3 waveguide etalon array which can be used as an optical frequency scale for the frequency standard for stabilization of a laser diode and the filter in the optical frequency domain. In a hybrid configuration made of cascaded fused quartz‐type branch guides, the resonant characteristics are evaluated. an etalon array filter characteristic with good waveguide uniformity is confirmed. Also, the stability of the fluctuation of each resonant peak frequency of the etalon array is evaluated with a frequency standard laser. In addition, a method is proposed for stabilization with a reference laser and an actual operation is confirmed. As a result, the frequency fluctuation of about 20 MHz with only the temperature control of 1/100°C is reduced to ± 2 MHz (corresponding to 1/1000°C) with stabilization by a reference laser. Further, an application example was presented when the present etalon array is used as a frequency substandard.