bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochromism of plasma‐polymerized Yb‐diphthalocyanine film in acidic electrolytes
Authors: Kashiwazaki Naoya
Published: July 2007

An electrochromic display (ECD) using a vacuumdeposited Yb‐diphthalocyanine film exhibits blue‐, greenand red‐colored states by its electrochemical reactions. When an acidic electrolyte was employed, the film exhibits a violet‐colored state and molecule dissociation without exhibiting a blue‐colored state. The stability of color change from green to blue in an acidic electrolyte was improved by usiag a plasma‐polymerized Yb‐diphthalo‐cyanine (pp‐YbPc2) film. The polymeric structure prevents pp‐YbPc2 from dissociation. In using the pp‐YbPc2 film with an acidic electrolyte, the durable ECD was found to be fabricated with a rapid response and high quality.
Temperature dependence of gray‐scale transmittance of thin‐film transistor LCDs driven by the frame rate control method
Authors: Tanaka Takeshi , Ono Kikuo , Konishi Nobutake
Published: July 2007

The temperature dependence of transmittance through a liquid crystal driven by the frame rate control (FRC) method was measured, where two‐level voltages (on/off) were supplied alternatively at intervals of a frame period for gray‐scale representation. The measurements were performed between 0 to 60°C on a 10‐inch diagonal thin‐film transistor LCD (TFT‐LCD) with a TN liquid crystal of normally white mode. The transmittance, with an on‐state voltage supplied in one frame period in every three periods, increased to 57 percent from 10 percent by increasing the temperatures to 60°C from 0°C, while the transmittance of the gray scales by the conventional method which use intermediate voltages show contrary dependence.

Since the transmittance was constant as long as the ratio of the response time of liquid crystal to the frame period was kept constant, the transmittance change was attributed to the increase in the response time with temperature. The temperature dependence of the FRC‐driven LCD was well simulated by considering the change in viscosity of the liquid crystal. It was found also that the transient change in the capacitance of the liquid crystal affects the transmittance characteristics.
Multidimensional optical interconnections using beam‐scanning laser diodes
Authors: Itoh Hideo , Mukai Seiji , Watanabe Masanobu , Yajima Hiroyoshi
Published: July 2007

Self‐routing optical spatial interconnections are more flexible than those of fixed‐routing. A beam‐scanning light source is effective for self‐routing interconnections.

This paper proposes optical buses and optical data links using far‐field beam‐scanning laser diodes (BSLD). Principles and characteristics of a fringe‐shifting laser diode (a new type of BSLD) are described. Multiple peaks of the fringes are useful for a spatial optical bus interconnection.
Frequency analysis of IC package inductance by the partial element equivalent circuit (PEEC) method
Authors: Nakamata Katsuro , Nishimura Michiaki
Published: July 2007

The recent advancement in ICs toward higher speed and higher density resulted in problems of packages such as delay in signal pulses, increase in noise, etc. To suppress this type of noise, one has to reduce the inductance, capacitance, and resistance of wires associated with the package. Numerical simulation is an effective approach for efficiently finding a wire pattern which gives the minimum values for these circuit elements. Little analysis has been conducted for effective inductance dependent on current distribution because the wires inside the package have complex three‐dimensional structures.

This paper describes a simulation system for current distribution and effective inductance. The system uses the partial element equivalent circuit (PEEC) method of calculating current flow in conductor segments. An actual package was analyzed with this simulator. It was shown that the simulated effective inductance as a function of frequency matches the measured value very well. It also was observed how the current distribution inside the conductor varies as the frequency changes. These results confirm the effectiveness of this method in analyzing the current distribution in, and the effective inductance of, package wires.
Simulation of head wear and reproduction envelope by the finite element method
Authors: Mizoh Yoshiaki , Yohda Hiroshi , Kita Hiromi , Kotera Hidetoshi
Published: July 2007

The computational analysis of head wear and the deterioration of the reproduced envelope were studied. The flexible tape was modeled as a thin anisotropic shell and the air‐film was treated by the modified Reynolds equation in the finite element method (FEM). Head wear was calculated by assuming an amount of wear which was inversely proportional to the square of the spacing. The reproduced envelope was calculated from the tape‐head spacing on the gap between the inlet site and the outlet side along the drum rotation. Good agreement between the calculation and the measurement was obtained. The transverse direction stiffness of the tape has a dominant effect on the envelope.
High‐speed LED/PD arrays for optical parallel interface
Authors: Uji Toshio , Fukushima Kiyoshi , Hayashi Junji , Watanabe Isao , Nagahori Takeshi , Ito Masataka
Published: July 2007

Optical parallel transmission is an effective technique for various interconnections, e.g., the interface between computer equipment. Monolithically integrated optoelectronic arrays for this purpose are very promising to realize compact, low power‐consuming, highly reliable, and low‐cost systems.

In this paper various devices are examined and compared in terms of the forementioned requirements. As the most suitable optical devices, a 12‐channel, 1.3‐μm mesa‐structure planar LED array with high output power at low drive current and a low crosstalk InGaAs pin‐PD array with separated‐unit structure have been developed. Coupled with the GI 62.5 multimode optical fiber, the output power, rise time and fall time of the LED array were ‐16 dB, 2.7 and 1.5 ns, respectively, at 12‐mA drive current.

Because of the low‐current operation, the interaction among channels due to heat generation was negligible. A separated‐unit structure was used for PD array to suppress crosstalk. As a result, the capacitance between two channels was as low as 0.05 pF, leading to the measured crosstalk lower than ‐40 dB until hundreds of megahertz 7‐mm thick compact modules with 1.5‐W power consumption have been fabricated and optical parallel transportation of 12‐channel, 150‐Mbit/s/ch for 100‐m distance has been realized with the modules.
An electroacoustic surface‐wave convolver of fabricated from a thin piezoelectric film and a semiconductor
Authors: Yamanouchi Kazuhiko , Kadosawa Fumio
Published: July 2007

A surface acoustic wave convolver composed of ZnO with high piezoelectricity and GaAs with high mobility is thought to be a highly efficient active device, and considerable work and development has been carried out on this device. However, no theoretical analysis which takes into account every parameter such as the dependencies on ZnO film thickness and carriers in GaAs has been carried out.

In this paper, the propagation characteristic of the surface acoustic wave in the ZnO/GaAs system was analyzed theoretically, taking into account the semiconductor carrier concentration in order to clarify the dependencies of the convolution efficiency of a ZnO/GaAs convolver on the ZnO film thickness, carrier density, and mobility. In addition, the dependencies of the convolution output on the surface acoustic wave oscillation characteristic in the ZnO/GaAs system and carrier density will be shown.
Analysis of ti‐diffused linbo3 optical waveguides by a modified step segment method
Authors: Kitoh Tsutomu , Kawano Kenji
Published: July 2007

In this paper, the modified step segment method (MSSM) is proposed as the highly accurate procedure in the analysis of the diffusion‐type optical waveguides and its accuracy is discussed theoretically. An optical directional coupler with exponential refractive index distribution is treated for which the numerically determined guided modes are compared with the analytical ones. As a result, it is found that the effective refractive index determined by MSSM agrees with the theoretical one and the error is less than 10−6.

It also is understood that the convergence of the method is much better than that of the step segment method (SSM). Comparison of the present method with the linear segment one (LSM) indicates that the overflow can be avoided together with a considerable shortening of the CPU time. Therefore, it is concluded that the present method is very effective in the analysis of the diffusion‐type optical waveguides with very high accuracy.
A novel digital signal processing bit synchronizer for a prml recording channel
Authors: Yada Hiroaki , Hayashi Nobuhiro , Yamakoshi Takamichi
Published: July 2007

The partial‐response maximum likelihood (PRML) system currently is investigated for practical applications as a modulation/demodulation scheme for digital magnetic recording equipment.

This paper proposes a construction of the bit synchronizer by complete digital signal processing. The operational principle is verified by experiment. The proposed bit synchronizer is composed of the decision‐feedback digital PLL and the interpolator. The decision‐feedback digital PLL receives the data‐asynchronous sampled signal sequence as the input, which is the result of sampling by the fixed clock of two samples/bit, and regenerates the clock. The interpolator calculates the signal value at the data point indicated by the phase of the decision‐feedback digital PLL output. The result is given to the Viterbi decoder.

By applying the proposed scheme, the PRML demodulator from the equalizer to the Viterbi decoder can be realized as a digital signal processing circuit, which operates synchronously with the single fixed master clock. A PRML demodulator is constructed based on the proposed bit synchronizer, and the operational principle is verified by an experiment using a magnetic disk device. The bit‐error rate less than 10−6is obtained for the channel bit rate of 10 Mbps.
High‐frequency properties of nbn(g)/al nanobridge‐type josephson mixers
Authors: Wang Zhen , Kawakami Akira , Komiyama Bokuji , Hamasaki Katsuyoshi , Matsui Toshiaki
Published: July 2007

To reduce the self‐heating effect and thermal noise in bridge‐type Josephson mixers, all‐NbN nanobridges with an Al “direct shunt” resistor were fabricated.

This paper describes the millimeter‐wave response and mixing properties of the NbN(g)/Al nanobridge‐type Josephson mixers in the 100‐GHz frequency. The effective noise temperature TNeff of the nanobridges was decreased to the bath temperature (liquid helium temperature, 4.2 K) by the Al “direct shunt” resistor and the millimeter‐wave induced steps were clearly observed at higher voltage (∼4 mV) than in the nanobridge without the Al “direct shunt” resistor.

The millimeter‐wave current dependence of the height of the millimeter‐wave induced steps was analyzed quantitatively, taking into account the thermal noise in the RSCJ model. The simulated result agreed with the experimental result very well. The systematic decrease of the induced step height with an increase of millimeter‐wave current was explained as the increase of effective noise temperature due to absorption of millimeter‐wave power. In the 100‐GHz Josephson mixing experiment, a large IF power output was obtained at a voltage up to about 1.6 mV. The effective noise power NEP and conversion efficiency were about 3 × 10−20 W/Hz and 0.2, respectively.
Directional coupler‐type wavelength filters having an integrated multiple‐waveguide structure
Authors: Shimada Kazuhiko , Kambayashi Toshio
Published: July 2007

This paper proposes an optical filter consisting of GaInAsP/InP waveguides whose performance is examined analytically. This filter is composed of a vertical three‐ or four‐waveguide directional coupler. Based on an eigenmode analytical method, a compact and demultiplexing device is realized. The propagation characteristics of such devices are calculated as being expressed in terms of the superposition of the eigenmodes.

A design criterion for both a demultiplexer and bandpass filter is presented. The demultiplexing of the two wavelengths of 1.545 and 1.585 μm with a crosstalk level better than ‐23 dB at a coupling length 265 μm is demonstrated. Also, with a multiple quantum well waveguide, a value of 6.9 nm for the ‐15 dB bandwidth at a coupling length 972 μm is obtained. Furthermore, the demultiplexing of the three wavelengths of 1.51, 1.545, and 1.60 μm is found to be possible in a four‐guide coupler structure (coupling length 942 μm) with MQW waveguides.
Autostereoscopic 3‐D display using LCD‐generated parallax barrier
Authors: Isono Haruo , Yasuda Minoru , Sasazawa Hideaki
Published: July 2007

A newly developed liquid crystal display‐generated (LCD‐generated) parallax barrier method for an autostereoscopic three‐dimensional (3‐D) display is described. This system consists of two LCD panels constituting a 3‐D display and a slit barrier. Compared to a conventional parallax barrier method, the slit barrier is not fixed but variable electrically. Therefore, the method can be flexible for any desired multiviewpoint 3‐D image display system. The compatibility with the usual 2‐D image display is fully ensured. Also, both 2‐D and 3‐D images can simultaneously be displayed. A prototype 3‐D image display apparatus suitable for a personal computer has been demonstrated to indicate a strong feasibility for a new 3‐D image display application.
Two‐port crystal resonator for high‐precision oscillator
Authors: Ueno Yoshifusa
Published: July 2007

A change of the oscillation frequency of an oscillator has commonly been achieved by changing the load capacitance of a crystal oscillator. Since the frequency changes nonlinearly with load capacitance, the rate of the frequency change varies with load capacitance. Therefore, when the frequency change through aging effects and/or due to the change in load capacitance occurs in TCXOs and VCTCXOs, the frequency shift must be compensated. However, the amount of compensation would be different before and after its adjustment.

This paper describes a newly developed two‐port crystal resonator. This resonator has two independent load capacitances so that the frequency response and the oscillation frequency shift due to a temperature and/or capacitance fluctuation can be compensated independently. This function cannot be achieved in a conventional oscillator which has only one load capacitance.

A formula to calculate the rate of a frequency change due to temperature and capacitance fluctuation has been derived by using the equivalent circuit of the two‐port crystal oscillator. The calculated value was found to be in good agreement with experimental result by taking into account stray capacitance. Therefore, this formula is useful for designing a two‐port crystal oscillator.
a‐SI TFTS with Stacked Gate Insulator of CVD‐SiO2/PECVD‐SiNx
Authors: Fukuda Kaichi , Ibaraki Nobuki
Published: July 2007

A‐Si thin‐film transistors (TFTs) with a stacked gate insulator of thermal CVD‐SiO2/PECVD‐SiNxwere developed. In an a‐Si TFT, the threshold voltage (Vthshifts when the gate is biased for a long time. The stability ofVthis influenced strongly by the characteristic of the gate insulator. Therefore, the high quality of the gate insulator is essential to achieve high performance in a TFT.

When an SiO2film is formed by thermal CVD, the invasion of nitrogen to the SiO2film is minimized and the defect density is lower than in plasma‐enhanced chemical vapor deposition (PECVD)‐SiO2. The properties of a TFT are strongly dependent on the SiO2deposition temperature and is improved by increasing the deposition temperature.

When the gate SiO2was deposited at 430°C, the field effect mobility μ was about 1 cm2/Vs and theVthshift was greatly reduced. It is expected that theVthshift in a TFT with a thermal SiO2gate for LCD driving is one‐third that in a TFT with a PECVD‐SiOxNygate used for the same purpose. Using the former TFTs, the time‐dependent degradation of LCD due to the degradation of the subthreshold characteristic of TFTs was largely reduced.
Present status and future of driver LSI
Authors: Saitoh Sei , Ikeda Naoyasu
Published: July 2007

Liquid crystal displays (LCDs) presently are used for display applications in many fields. New areas of interest for LCDs include how to cope with the large size, high resolution, multiple color, low power consumption, small thickness, and applications to multimedia. The keys to these subjects are the driving methods and driver LSIs. It is not too much to say that the driving method and display quality of LCD are determined by driver LSIs. In particular, driver LSIs are extremely important in realizing multiple color displays.

This paper describes the present status and future of driver LSIs for driving full‐color, thin‐film transistor (TFT)‐LCDs for OA applications.
Inverse‐staggered polycrystalline silicon thin‐film transistors fabricated by excimer laser irradiation
Authors: Ono Kikuo , Ogawa Kazuhiro , Sakuta Hiroki , Konishi Nobutake
Published: July 2007

Fundamental device performance, mobility distribution, and threshold voltage shift characteristics of inverted staggered polycrystalline thin‐film transistors (TFTs) are discussed. The present TFT uses a polycrystalline silicon (p‐Si) crystallized by excimer laser as semiconductor layer and SiN prepared by CVD method as gate insulator. The TFT was fabricated onto glass substrate of 100 mm2at a maximum temperature of 300°C. Measurements of the distribution of mobility were carried out with devices placed at every 0.3 mm pitch. As a result, the mobility μ of TFT made at laser intensity of 200 mJ/cm2is 20.9 cm2/V · s and the off‐current is 2 × 1011A. TFT was found to be very uniform except for a region where a superposition of 200 mJ/cm2laser irradiation over a weak laser intensity was made.

The analysis indicates that the region for low micrometer is the area irradiated by a laser intensity 110 to 170 mJ/cm2. The region irradiated with laser intensity of this range also was found to be in a mixed state of amorphous silicon of depleted hydrogen atoms and crystalline consisting of fine grains. A shift voltage at 20 V gate dc voltage at 104s after the application of the voltage is 0.2 V, 1/25 time smaller compared to a‐Si TFT. The presentp‐Si TFT is demonstrated to exhibit high‐device performance for liquid crystal display.
A new two‐dimensional analysis method for polycrystalline‐silicon tfts
Authors: Yamada So , Kato Noriji , Koyanagi Mitsumasa
Published: July 2007

A new device simulation method for polycrystal‐line‐silicon thin‐film transistors (denoted as poly‐Si TFTs) is developed. The method is suitable to estimate the TFT characteristics and to analyze the operation mechanisms. In this simulation the influences of grain boundaries are incorporated into the carrier mobility model and the two‐dimensional distributions of the electrostatic potential and carrier concentrations are solved numerically.

This simulation has enabled the quantitative evaluation of the dependences of TFT characteristics on grain size and grain boundary trap density, and the current‐voltage characteristics obtained as a result are in good agreement with the measured characteristics over a wide range from the on‐state region to the subthreshold region. Furthermore, in combination with the carrier generation model, high‐field phenomena such as the kink effect and avalanche breakdown can be analyzed in detail.

By analyzing the mechanism of short channel effects that are inherent in poly‐Si TFT using this simulator, this effect has been attributed to the accumulation of carriers generated by avalanche in the poly‐Si thin film.
Analysis of microstrip crossovers using the nonorthogonal finite‐difference time‐domain method
Authors: Kitamura Toshiaki , Nakamura Satoru , Hira Masafumi , Kurazono Sadao
Published: July 2007

Multilayered monolithic microwave integrated circuits (MMIC) have been proposed with a view to reducing the size and increasing the degree of integration of the MMIC. It has been demonstrated that new circuit configurations can be realized and the design capability can be improved. By the use of a multilayered MMIC, the circuit can be laminated so that the circuit size can be made smaller. However, since the circuit is laminated, qualitative evaluation of the crosstalks between the upper and lower transmission lines becomes important. Most of the previous analyses on the microstrip line crossover focused on the case where the two lines cross orthogonally.

In this research, the finite‐difference time‐domain (FD‐TD) method applicable to an arbitrary coordinate system is used for the analysis of the crosstalk when two transmission lines cross at an arbitrary angle.

First, the FD‐TD method that can be applied to an arbitrary coordinate system is summarized. Next, it is confirmed that the results of the present analysis for a single microstrip line do not depend on the mesh shape and that the present analysis results agree with those by other methods for a microstrip bend with an arbitrary angle. Finally, a three‐dimensional crossover of micro‐strip lines with an arbitrary angle is analyzed. the normalized frequency characteristics, cross‐angle dependence, and the interdistance dependence of thesparameters are presented.
Miniaturization of 35‐GHz NRD‐guide transmitter and receiver
Authors: Uchida Izumi , Kuroki Futoshi , Yoneyama Tsukasa
Published: July 2007

The performance of the 35‐GHz nonradiative dielectric waveguide (NRD‐guide) transmitter and receiver has been improved and they have been reduced in size. the miniaturization of the transmitter has been proposed by reducing the size of the terminator. Since the reflection of the balanced mixer for heterodyne detection has been reduced, miniaturization of the receiver is obtained by removing the circulator used for protection from reflection. the new transmitter and receiver are reduced to half their earlier sizes. Their frequency stability is less than −0.6 ppm/°C. Moreover, horn antennas with rigidity and air tightness are connected to the transmitter and receiver.
Development and application of optical shutter made of PLZT ceramics
Authors: Seino Taisaku , Watanabe Michihiro
Published: July 2007

Using PLZT, which is a transparent ceramic with an electrooptical property, an electrooptical device for high‐speed modulation was fabricated. PLZT was synthesized by the oxide mixing method and the oxalate method in ethanol solution.

Using ethanol as a dispersion medium in the former method, the grain size which strongly influences the transmittance can be controlled. the structure of the optical shutter made of PLZT was determined by investigating the electric field distribution in the unit device forming the shutter by the finite element method. Then the optical shutter was formed by patterning the PLZT wafer using photolithography.

A three‐dimensional (3‐D) image display system by stereoscope was constructed. the PLZT device was capable of switching display image at 60 and 120 Hz. This device was also usable for 3‐D image display.
Optmum design of low‐voltage and high‐efficiency GaAs power module
Authors: Maeda Masahiro , Ota Yorito , Ishikawa Osamu
Published: July 2007

A highly compact GaAs power module designed for the portable analog telephone system has been developed [1]. the module is a two‐stage GaAs power amplifier operable at 4.7 V and is capable of delivering an output power of 32.2 dBm with a power‐added efficiency of 65 percent and harmonic levels less than −40 dBc at 900 MHz.

Parameter extraction from two GaAs MESFETs (first‐ and second‐stage FETs) operable at 4.7 V, module design employing a front stage FET whose output characteristics are optimized at a load of 50 ω, and the optimization of harmonic control circuit suppressing the harmonics and improving the drain efficiency are performed by simulation and the obtained results are confirmed by experiments.
Saw filters for high‐power use in cellular radio portable phones
Authors: Hikita Mitsutaka , Shibagaki Nobuhiko , Akagi Takatoshi , Sakiyama Kazuyuki
Published: July 2007

Before a SAW filter is applied to the high‐power section of a cellular radio portable phone, it is necessary to develop a higher‐performance filter with a high‐power capability and a small, nonlinear effect. In this paper, as a new type of filter, a SAW resonator coupled filter of an extended type is proposed which uses two types of piezoelectric substrates. A design method considering the impedance matching between the substrates is presented as well as the results of the experimental duplexer satisfying the specifications of the cellular radio portable phone for the United States. This filter has a third‐order nonlinearity effect that results in the spurious response sensitivity much smaller than the conventional transversal type. These characteristics are almost identical to those for the present dielectric resonator duplexer for the forementioned use.
Basic properties of anodized porous silicon formed under uniform current density
Authors: Aoyagi Hidekazu , Motohashi Akira , Kinoshita Akira , Aono Tomoyoshi , Satoh Akinobu
Published: July 2007

Porous silicon is formed by anodization of single crystalline silicon under various current densities and HF concentrations which are the important parameters for anodization. Anodization is carried out in HF solution at constant temperature under a constant current density distribution.

This paper describes the fabrication process dependencies of dissolution valence, porosity, and layer formation efficiency which are related directly to the anodization conditions. In addition, the mechanical strength of porous silicon obtained by the hardness measurement was related to the self‐standing limit of porous silicon obtained by a cylindrical model for pores arranged in the twodimensional lattice.
Analysis of thermoelectric power generation using thermoelectric element
Authors: Ogawa Yoshihiko , Watanabe Hideo , Sakai Motohiro , Tunou Katsuhiro
Published: July 2007

Recently, there has been renewed interest in the thermoelectric power generation based on the thermoelectric element with a view to the recycling of wasted heat. the existing theory on this subject, however, has been derived from a macroscopic viewpoint such as thermal balance. Since no differential equation is solved, it was not possible to analyze even fundamental subjects such as derivation of the temperature profile inside the element.

In this paper, by means of a newly derived nonlinear thermoeleetric differential equation, the temperature profiles and generated output power are analyzed accurately with actual material data. From the analysis, various conclusions are derived. Further, the analysis results by a differential equation which is a linear approximation of the original nonlinear equation are compared with those of the nonlinear equation. It is shown that good agreement is obtained. Also, the previous theory is compared with the analysis results of the linear differential equation. It is pointed out that the previous theory has a certain degree of validity.
Characteristics of a Čerenkov laser improved by loading a kerr‐like medium
Authors: Shiozawa Toshiyuki , Utsunomiya Eiji , Ueda Tetsuya
Published: July 2007

In the čerenkov laser, as the electromagnetic wave grows by gaining energy from the electron beam, it loses kinetic energy and, thus, its drift velocity decreases. As a result, the synchronism between the propagation velocity of the electromagnetic wave and the drift velocity of the electron beam ceases to be kept and efficient growth of the electromagnetic wave is prevented. to overcome this difficulty, this paper proposes a model for the čerenkov laser loaded with a Kerr‐like medium, the permittivity of which increases in proportion to the square of electric field. Also, a numerical investigation is made to determine how the growth characteristics for the electromagnetic wave are improved with the aid of the finite element method.

The numerical result shows that, by choosing a proper value for the nonlinear coefficient of the Kerr‐like medium, the propagation velocity of the electromagnetic wave can be delayed in accordance with the decrease in the drift of the electron beam. Thus, the growth characteristics for the electromagnetic wave can be improved greatly. In addition, it is found that the interaction distance to maximize the electromagnetic wave power extracted from the electron beam can be shortened compared with the case where only a linear dielectric is loaded.
Temperature dependence of led intensity due to filter effect of Sinx
Authors: Toyama Toshihiko , Tanaka Yukio
Published: July 2007

The filter effect of an SiNx film used to passivate a light‐emitting diode (LED) was investigated. the transmission spectrum of an SiNx film is dependent on the film thickness, while the wavelength of light emitted from an LED depends on temperature. Therefore, the intensity of emitted light depends on the temperature characteristic of the thickness of the SiNx film. LEDs with SiNx films whose thicknesses were (3/4 + 15%) λ were realized.

The simulation indicated that the content of the temperature coefficients of emission intensity due to the filter effect was between −0.049%/°C and +0.072%/°C when the thickness of the SiNx was varied as described in the foregoing. On the other hand, the experimental results on the variation of the temperature coefficient due to the filter effect was between −0.01 %/°C and +0.03%/°C. In this study, the agreement between the simulated and experimental results were not in quantitative agreement because the temperature coefficients of the LEDs were not uniform in comparison with the component due to the filter effect.
Analysis of marks recorded on magneto‐optical media by the magnetic field modulation method
Authors: Shibuya Giichi , Matsumoto Mitsunori , Morisako Akimitsu , Shibahara Masanori
Published: July 2007

The readout signal waveform and recorded mark of magneto‐optic write media are investigated using the magnetic field modulation method. Because overwrite is possible in the magnetic field modulation method, it has been applied to a small magneto‐optic disk in a new audio media system. the magneto‐optic mark recorded by this system has a chevron shape, and the width is highly sensitive to changes in such factors as laser power or ambient temperature. For this reason, it is necessary to design the recording medium so that a sufficiently stable readout signal is obtained for these changes.

A numerical integral obtained by polygonal approximation of recorded mark is used, and the readout signal waveform is determined by simulation. By this technique, the readout signal amplitude and crosstalk level that influence the medium and the recording density are determined. Based on this result, the write density of the medium is computed and comparison with measurement values indicates that agreement is excellent. Moreover, by adjusting the tracking offset during readout, it is possible to improve the apparent write power margin. Thus, the technique will be very effective in the design of future high‐density recording media.
Fractal analysis on pore structure for activated carbon fibers
Authors: Endo Morinobu , Takeuchi Kenji , Sasuda Yoshihiro , Matsubayashi Ken'Ichi , Oshida Kyoichi , Dresselhaus Mildred S.
Published: July 2007

Recently, the active carbon filter (ACF) has drawn attention because of its usefulness in the electrical and electronics fields. to improve the quality of ACF, the microscopic structure of this material must be analyzed. One method is to observe the structure using a transmission electron microscope (TEM).

Recently, the capability of the TEM has been improved drastically. Not only can its molecular structure be observed but also numerous analytical equipment has been attached to it. ACF has been investigated by using a TEM, and it has been found that the ACF structure was so complex that quantitative analysis was impossible.

Computer analysis of a TEM image has also been attempted. In this analysis, the TEM image was processed by the two‐dimensional fast Fourier transform and fiequency analysis to investigate the distribution of the pore diameter of ACF. As a result, it was speculated that the pore shape was fractal. Then, it was shown that the contour of the pore cross section was fractal and the fractal dimension was obtained. When the structure was too complex to analyze only by TEM analysis, the introduction of the image processing method was effective.
A branch‐line eight‐port hybrid circuit
Authors: Kawai Tadashi , Lio Ken'Ichi , Ohta Isao
Published: July 2007

This paper deals with a circuit in which a total of eight ports made of two sets of four ports are mutually separated and in which the input from one port is delivered to four ports of another set with equal amplitudes with a certain phase relationship. This circuit is called the eight‐port hybrid circuit and is an extension of the characteristics of a conventional (four‐port) 3‐dB hybrid to the case of eight ports. A circuit configuration is proposed by means of four branch‐line‐type 3‐dB hybrids.

First, by taking advantage of the symmetry of the circuit, an analysis is carried out. the relationship to be satisfied by the characteristic admittances of each branch line is determined. the frequency characteristics of the scattering matrix elements are presented.

Next, a design method for broadening the bandwidth is given for the matching circuits to be attached to each port and quarter wavelength transmission lines connecting each hybrid. A relative bandwidth of about 20 percent is realized. Also, the test circuit is measured and the validity of the design method is confirmed. the present circuit is advantageous in that the circuit configuration is possible on one side of the substrate by means of strip lines and all eight ports are directed outward so that connection with other circuits is simplified.
Fabrication ofpin/hemt receiver oeics for Gb/s lightwave systems on three‐inch diameter inp substrate
Authors: Yano Hiroshi , Doguchi Kentaro , Murata Michio , Nishiyama Naoki , Sasaki Goro , Hayashi Hideki
Published: July 2007

Receiver optoelectronic integrated circuits (OEICs) have been successfully designed on a three‐inch diameter InP substrate. Epitaxial layers grown by OMVPE on three‐inch diameter InP substrates showed good uniformity of electrical and optical properties. By using the epitaxial layers, transimpedance‐type receiver OEICs were fabricated. the receiver OEICs over a three‐inch diameter InP substrate showed an average bandwidth of 2.78 GHz with a standard deviation of 280 MHz. the receiver also exhibited a transimpedance of 61.1 dB and a sensitivity of ‐24.9 dBm for 2.4 Gb/s input signals. These results indicate that the receiver OEICs designed on a three‐inch diameter InP substrate are ready for practical use in Gb/s lightwave systems.
Integrated coupling device between a laser diode and an optical fiber using a microlens
Authors: Shimada Jun‐Ichi , Ohguchi Osamu , Sawada Renshi , Tanaka Hidenao , Watabe Akinori
Published: July 2007

An integrated coupling device between a GaAs/Al‐GaAs laser diode and an optical fiber using a microlens is described. It is calculated that the high single‐mode fiber coupling efficiency of 81 percent is obtained for the microlens with RMSA of 0.4 λ and that the large alignment tolerance of 55 μm is obtained in thez‐direction. It is demonstrated experimentally for single‐mode fiber coupling that the coupling efficiency is 26 percent and that the alignment tolerance in thez‐direction is 19 μm. the differences in the coupling efficiency and alignment tolerance between the calculation and experiment are due to a mismatch of beamwidth and the fabrication error of the fiber guide. Additionally, measurement of the oscillation spectrum of this coupling device, which has a composite cavity, showed that an LD with a microlens and fiber causes multimode oscillation due to reflection from the fiber facet.
Integrated optic grating scale‐displacement sensor using linearly focusing grating couplers
Authors: Ura Shogo , Shinohara Masayuki , Endoh Toshiaki , Hiroshi Nishihara Toshiaki Suhara
Published: July 2007

An integrated optic sensor was proposed and demonstrated for measuring displacement of a grating scale. the sensor is constructed by integrating a pair of linearly focusing grating couplers (LFGCs) and a pair of photodiodes (PDs) in a glass waveguide on an Si substrate. Two beams, radiated from the LFGC pair, overlap on the grating scale with each other. the beams diffracted by the grating scale interfere on the PDs, and the interference signals vary when the grating scale moves along its grating vector direction. the device was designed and fabricated, and the variation of output photocurrents was confirmed experimentally.
Realizing a completed‐resonant level by using an asymmetrical triple‐barrier structure
Authors: Ren Jie , Nagai Nobuo , Ohtani Naoki , Miki Nobuhiro
Published: July 2007

Because of the rapid development of quantum effect devices, it is necessary to obtain a synthesis method which can give the expected quantum effect symptoms. Using a triple‐barrier structure, quantum effects which cannot be obtained with a double‐bather structure can be realized. However, only a few studies have been made on the triple‐bather structure, in particular, on the asymmetric triple‐bather structure.

In this paper, based on the circuit theoiy, the syn thesis method of an asymmetrical triple‐barrier structure where a single perfect resonant level is formed in its quantum well is proposed. It is assumed that an original symmetrical double‐barrier structure has a first resonant level E1 and a second resonant level E2 whose resonant energy is four times higher than that of E1. One of the single barriers is replaced by another symmetrical double barrier with the first resonant level equal to the second resonant level E2 of the original one.

In the nonsymmetrical triple‐barrier structure formed by the forementioned method, the transmission probability at E1 is 1 and that at higher‐energy levels is sufficiently low. This synthesis can be achieved by using the power reflection coefficient and the Smith chart of a complex equivalent circuit. the validity of this method can be established by means of the Smith chart. By carrying out a numerical calculation on the electron transmission characteristic of the synthesized nensymmetrical triple barrier, it was confirmed that the transmission probability at the energy level that is four times higher than E1 can be around 0.1.
Design and operation of josephson circuits using ruffle gates with a stacked structure
Authors: Nagaishi Hideyuki , Nakahara Kouji , Hasegawa Haruhiro , Nishino Tosikazu
Published: July 2007

DC‐powered Josephson logic gates have the advan tage of being free from operation error due to crosstalk from power current in contrast to ordinary ac‐powered Josephson logic gates. One of these, the HUFFLE (hybrid unlatching flip‐flop logic element) gate using stacked Josephson interferometers (JI) can execute complicated logic functions by itself. Therefore, high‐Speed operation of logic circuits using HUFFLE gates may be expected because the number of logic stages in the circuits is reduced. to investigate the improvement in circuit per formance by using HUFFLE gates with the stacked structure, the authors have fabricated a 6‐bit arithmetic logic unit (ALU) and tested its operation. Two new logic gales, exclusive OR and majority, newly developed using the stacked structure have been developed. the ALU which performs the four functions, AND, OR, exclusive OR, and ADD, is realized with seven logic stages. Ac cordingly, reduction in the number of logic stages and execution time of the ALU by use of the stacked HUF FLE gate family is confirmed.
LiNbO3 optical waveguide devices
Authors: Minakata Makoto
Published: July 2007

This paper describes the present status of LiNbO3 optical waveguides with respect to the optical grade crystal, growth process, dc drift, and optical damage. In addition, the wideband optical modulators, QPM‐SHG blue light source and epitaxial growth of LiNbO3 are reported. Optical grade crystals are needed for devices described in the foregoing and the requirements for such crystals have been proposed.

The physics of optical waveguides has been understood and the relationship between the device properties and fabrication processes has been clarified. Methods to suppress the dc drift which has been one of the obstacles in practical applications of optical waveguides have been established. the solutions to minimize the optical damage in SHG devices have been found.

Recently, drift‐free optical modulators and wideband optical modulators for 70‐GHz applications have been reported. Because of the rapid progress in polarization inversion technologies, SHG devices for blue‐light emission with an output power of 20 mW and a conversion efficiency of 600 percent/Wcm2 have been developed. Solid‐state lasers formed by doping Er and Nd to crystals have been investigated. the research of growing an LiNbO3 thin film to form an optoelectrical integrated circuit has been carried out.
A solution method based on the coupled‐mode theory for natural single‐phase unidirectional surface acoustic wave transducers
Authors: Hasegawa Koji , Inagawa Kiyoshi , Koshiba Masanori
Published: July 2007

A method for analysis of natural single‐phase unidirectional transducer (NSPUDT), which is one of unidirectional surface acoustic wave interdigital electrodes, is proposed in which the mode coupling theory and the finite‐element method are used. the finite‐element method is used for calculations of the upper and lower limit frequencies of the stop band, the potential standing wave distribution at these frequencies, and the static capacitance per electrode pair for the short and open gratings corresponding to the electric terminals either shorted or open. In the substrate used for NSPUDT, the locations of the maximum and minimum of the standing wave in general vary in the depth direction of the substrate. Hence, it is not possible to use the standing wave pattern in the substrate as is used for a substrate surface where electrodes are present. the variation of the potential in the depth directional of the substrate is incorporated into the mode coupling theory in this research, so that the depth dependence of the standing wave profile is qualitatively evaluated. Hence, it is made possible to confirm the locations of the maximum and minimum of the standing wave at the substrate surface from the standing wave profile in the substrate.

Specifically, the present method is applied to NSPUDT on an ST‐cut 25deg; X‐propagation quartz substrate so that its validity and usefulness are confirmed.
Photonic networks
Authors: Miki Tetsuya
Published: July 2007

Optical communication systems underwent rapid development during the 1980s, and 10‐Gb/s systems are now being developed. Furthermore, asynchronous transfer mode (ATM) technology is being applied to the development of transport nodes with throughputs of 20 to 100 Gb/s for communications networks. However, such speeds are close to the limits of what can be achieved with systems based on electronic processing and, in the near future, it will become necessary to change over to photonic networks in which processing is done optically. Photonic networks are not just characterized by high speed and wide bandwidth; it is also possible to build them with a simple yet flexible configuration. This paper gives an overview of how photonic technology can be introduced in different parts of a network, including the core network, the access network, and private networks, and describes the areas requiring further research. Research into fundamental devices is also progressing, and research into photonic networks is also being actively pursued in the West. Photonic networks will form the foundation of wideband networks in the next century, and their research is extremely important.
Calculation of Q factor and treatment of curved conducting wall in cavity analysis by FD‐TD method
Authors: Lida Yukio , Morita Masanobu
Published: July 2007

In this paper, a method for computing a Q value is proposed, which is believed useful for a high Q cavity. In this method, the Q value is derived from the input excitation energy and the stored energy in the process of increasing amplitude of the electromagnetic field in the cavity. This method is applied to a rectangular cavity without an aperture and the Q value obtained has an error of only approximately 1 percent.

In this paper, a cylindrical cavity without an aperture is used as an example and the surface processing is investigated by means of the electromagnetic field distribution in the cavity and the wall loss. In the stair‐stepped approximation of the cylindrical wall surface, the electromagnetic field is disturbed significantly near the wall in the case of the TM010 and TM011 modes which have magnetic fields in the azimuthal direction. In addition, the Q value is higher by 21 × 32 percent and the computed wall loss is too small. Using CP method analysis, in which the integration path is modified to fit the boundary for wall processing, both the electromagnetic field and the wall loss are computed accurately.
Effects of space charge and multiple scattering on the gain of an X‐ray free electron laser using stimulated transition radiation
Authors: Yoshimori Shigeru , Kawamura Mitsuo
Published: July 2007

For the X‐ray free electron laser using stimulated transition radiation in periodic stacks of metal foils or polymer films, the effects considered are those that are due to: (1) the space charge of the relativistic electron beam; (2) multiple scattering of the electron beam passing through the stacks; and (3) both the space charge and multiple scattering simultaneously. Taking these respective effects into account in a Boltzmann transport equation, dispersion relations are derived and gain coefficients of the laser are calculated and compared. As a result, it is found that the effect of multiple scattering is large and it depends also on the magnitude of the electron beam energy, e.g., for the case of 50 GeV, the gain coefficient is decreased by several dB. The effect of the space charge is relatively small. Also, the gain coefficient generally decreases with the beam energy.
Multilayer monolithic microwave integrated circuit directional coupler using thin dielectric layers and its applications to millimeter‐wave circuits
Authors: Banba Seiichi , Minakawa Akira , Imaoka Toshikazu , Imai Nobuaki
Published: July 2007

A multilayer monolithic microwave integrated circuit (MMIC) directional coupler is proposed in which the characteristics of the multilayer MMIC structure constructed with conductors and dielectric films on a GaAs wafer surface are used effectively. In the proposed directional coupler, a tight coupling of 3 dB can be realized with low loss and in a small area. It is highly flexible in design. Also, it is shown in this paper that by means of the proposed multilayer directional coupler, a millimeter‐wave variable attenuator, a balanced modulator, and an endless phase shifter can be realized. These structures play important roles as millimeter‐wave amplitude/phase control circuits. Hence, it is significant to accomplish miniaturization and MMIC realization.

The multilayer directional coupler designed and fabricated in the 40‐GHz band exhibited a circuit area of 0.45 mm2and coupling losses of 4.0 ± 0.2 dB. The designed and measured values agree well. Further, the amplitude/phase control circuits were designed and also exhibited a good performance.