bluuebunny/crossref_metadata_2025 huggingface dataset:
Hybrid optical bistability in ferroelectric liquid crystal and its dynamic characteristics
Authors: Tagawa Akira , Moritake Hiroshi , Ozaki Masanori , Yoshino Katsumi
Published: July 2007

In the area of optical logic and optical information processing, such nonlinear optical devices as optical Instability, optical amplifier, and optical limiter are important basic elements.

In this paper, the hybrid optical bistability and optical limiter characteristics are realized by means of an electrical linear feedback to a ferroelectric liquid crystal cell (SSFLC cell). If the feedback gain is positive, the optical bistability is obtained while the optical limiter characteristics are obtained if the gain is negative. Also, it was demonstrated that by instantaneously increasing or cutting the incident optical intensity in a pulsed state in the optical bistability region, the transmission light intensity can be switched from the low‐transmission state to the high‐transmission state or from the high‐ to low‐transmission state. The minimum pulsewidth needed for switching is 70 μs for the low‐transmission state to the high‐transmission state and 50 μs for the high‐transmission state to the low‐transmission state. Since the speed is very fast, the high‐speed response of the ferroelectric liquid crystal is used effectively.
Development of a scanning‐type mie‐lidar system for global measurement of aerosol density in the atmosphere
Authors: Saito Yasunori , Iijima Ken , Kobayashi Fumitoshi , Nomura Akio , Kano Tetsuo
Published: July 2007

To understand the dynamic behavior of the aerosol density in the atmosphere, a Mie scattering lidar was fabricated. The system consisting of a YAG laser and a receiving telescope is scattered automatically in the horizontal direction with a stepping motor and enabled a global real time monitoring over a radius of 5 km. The measured results are displayed in an image as a global mapping chart of the aerosol density in the atmosphere. From the end of November 1989 to the present, steady measurement has been carried out twice a week. Interesting results have been obtained including the existence of a high concentration aerosol region along a major highway.
Instabilities and Their Characterization in Mach‐Zehnder Ti:LiNbO3 Optical Modulators
Authors: Jumonji Hiromichi , Nozawa Toshinori
Published: July 2007

For the Ti‐diffused LiNbO3 optical modulator, which is expected to be applied to optical communication systems and optical measurement instruments, quantization of various unstable phenomena degrading the practical operations is attempted. The characteristic parameters related to each phenomenon and their temperature dependence were measured under the condition of a constant optical output. The following observations were made:

(1) The polarity and the relaxation time of the short‐term dc drift (namely, the variation of the driving point immediately after the application of the dc bias) depend on the configuration of the buffer layer;

(2) The temperature drift (namely, the variation of the driving point due to that of the ambient temperature) is a short‐term drift phenomenon and its relaxation time is related to that of the short term dc drift;

(3) The long‐term dc drift (namely, the variation of the driving point over a long time) depends on the magnitude and polarity of the electric field applied on the waveguide region. Its relaxation time is much larger than those of other phenomena; and

(4) From the temperature dependence of the relaxation time of each phenomenon, it is found that their activation energies are almost equal and are about 0.7 eV.

Further, based on the equivalent circuit model newly proposed, the relationship among the parameters was evaluated. It is found that each unstable phenomenon can be explained by the equivalent circuit model in which the formation of the space charge layer is taken into account.
Three‐dimensional full‐wave analysis with nonlinearity and line characteristics of device by electromagnetic field analysis on time domain
Authors: Kimura Hideaki , Yoshida Norinobu
Published: July 2007

Recently, with the increased bandwidth and operating frequencies in the integrated circuits, the nature of the wave has begun to appear in the signals in the ICs. Therefore, it has become indispensable to use distributed circuit treatment of the circuits such as the propagation delay. Also, in the design of the circuit for a broadband and large signal operation, an analysis method is required in which both the distributed devices and the nonlinear devices are analyzed in a unified manner. A simple method for introducing the distributed effect in the nonlinear circuit analysis is to construct the interconnect with an LC ladder network and to carry out the calculation in the time domain. It is difficult to introduce the frequency dispersions of the transmission line.

On the other hand, the three‐dimensional full‐wave analysis is effective in the sense that the frequency dispersion due to the circuit configurations is taken into account automatically. Also, recently, the harmonic balance method has been introduced in which the nonlinear circuit analysis is conducted by separating the nonlinear and linear parts of the circuit. However, the number of harmonics to be considered is limited.

In this paper, with a view to circuit analysis containing the nonlinear devices and the distributed effect in the interconnect, nonlinear devices are included in the three‐dimensional time‐domain analysis methods such as the FD‐TD and spatial network methods. A systematic three‐dimensional full‐wave analysis is realized for the large signal operation of the circuit containing nonlinear devices.
Design of a thermal print head for high‐speed and high‐resolution printing
Authors: Shibata Susumu , Kanamori Takashi
Published: July 2007

Thermal analysis of a thin‐film thermal print head was carried out with the aim of obtaining guidelines for the design of a print head for high‐speed and high‐resolution printing.

The analysis showed that if current is passed through the heating resistors for a short period, there will be a time lag between the temperature increase in the resistors and the temperature increase in the heat sensitive paper. Furthermore, although a short pulse is preferable for high‐resolution printing, there is a point beyond which further decrease in the duration of the pulse has little effect.

It was estimated that changes to the heat insulation layer and protective film alone would not lead to an improvement in the performance of the print head as a whole. The printing test yielded the same results as those provided by the thermal analysis. For example, a pulse duration of 5 ms is not preferable for a resolution of 16 dots/mm. However, the contrast obtained with a pulse duration of 0.3 ms may also be obtained with a pulse duration of 0.8 ms.
Resolving power of infrared upconverter‐spectrometer using rotation of a medium with periodic variation of nonlinear coefficients
Authors: Koyanagi Kojiro
Published: July 2007

As an application to the upconverter which converts infrared light to visible light by means of a three‐wave sum frequency conversion, an infrared upconverter‐spectrometer is proposed which uses rotating scanning of a periodic nonlinear medium (consisting of layers of media with the sign of nonlinear optical coefficient alternately inverted). In this structure, the wavelength selection capability of the phase matching in the parametric interaction is used. The resolving power and the maximum output (conversion efficiency), which are important basic characteristics in the infrared upconverter‐spectrometer, are studied theoretically. The resolving power versus the incident angle of the pumping light is studied in detail with the medium dispersion and the two‐dimensional size taken into account.

As examples, the infrared upconverter‐spectrometers for 10‐ and 3‐μm bands using GaAs and LiNbO3 as the periodic nonlinear media have been considered and their resolving power has been derived numerically. Excellent visible detectors can be used in these infrared spectrometers. In addition, they can use isotropic media with ordinary dispersion and large nonlinear optical coefficients. By means of rotating scanning of the crystal, they can have high sensitivity and high response time. Depending on the direction of incidence of the pumping light, a resolving power higher than that of conventional structures can be obtained.
Automatic synthesis of holographic stereograms with ray‐traced image data
Authors: Kinoshita Kenji
Published: July 2007

An automatic synthesizing method of holographic stereograms (HSs) has been studied for computer‐graphic images, and experimental results of image reconstruction have been presented. In the synthesis of the HSs, raytraced image data of 180 frames were generated, changing a viewpoint. Then these data were recorded on a holographic film of about 70 mm x 300 mm using a liquid crystal television panel as a spatial light modulator. The fabrication time of one HS was about 50 min. In image reconstruction with a 5‐mW He‐Ne laser, it has been possible to display three‐dimensional images which have a good parallax effect.
The I‐V characteristics of polycrystalline silicon diodes and the energy distribution of traps in grain boundaries
Authors: Yamamoto Ichiro , Takeda Ryo , Suzuki Yoshihisa , Kuwano Hiroshi , Saito Yoji
Published: July 2007

The current‐voltage characteristics of p+pn+ structure polycrystalline silicon diodes and the energy distribution of traps in the grain boundaries are measured before and after plasma hydrogenation. Plasma hydrogenation increases the forward current and reduces the reverse current. The energy distribution of nonhydrogenated film has a peak around the midgap; this peak disappears after hydrogenation. The change in diode current produced by plasma hydrogenation can be explained by this difference in the energy distribution of the traps.
Characterizations and growth mechanisms of the surface‐oxidized layer formed on Al‐Nb‐(N) alloy films
Authors: Noya Atsushi , Sasaki Katsutaka
Published: July 2007

The oxide growth and the characterization of a thin protective layer peculiar to an aluminum surface have been examined by varying the composition of Al‐Nb alloy films and by nitrogen doping. At room temperature, an aluminum oxide layer was formed on an Al‐Nb alloy surface by preferential oxidation. In the Al‐Nb alloy with an Al‐rich composition, Nb underneath the oxide layer was not oxidized, while in the alloy with an Nb‐rich composition, oxidized Nb was present on the oxidized surface layer even at room temperature and the oxidized layer grew as the temperature increased.

The lower oxides of Nb which were already present at room temperature enhance the oxidation of Al, causing a decrease of the activation energy for oxidation. As a result, the oxidized layer grows as the temperature increases. To confirm the presence of activation process of Al oxidations by impurity doping, an Al‐rich alloy was doped with nitrogen. The result shows that a similar activation process accelerates the oxide growth by nitrogen doping. It was then concluded that the possible activation process of the Al cations is involved in the mechanism of losing the protectivity in the Al oxide.
Wafer‐to‐wafer temperature distribution control in a diffusion furnace
Authors: Matsuba Ikuo , Mokuya Kinji , Matsumoto Kuniaki , Yoshinaka Akira
Published: July 2007

A control scheme to achieve wafer‐to‐wafer temperature uniformity in the reaction tube used for oxidation, diffusion, or annealing during semiconductor processes is proposed. In the analytical model, self‐radiation loss, radiation between neighboring wafers, radiation from the tube wall, and thermal diffusion on a wafer surface are taken into account. The temperature monitoring points were the inlet, middle, and outlet of the reaction tube.

The analysis indicates that if the tube wall temperatures at the inlet and outlet are 6 percent higher than that at the center of the tube, the wafer‐to‐wafer temperature becomes uniform. In the experiment, taking the silica tube temperature as the tube wall temperature, the increase in the temperatures at the inlet and outlet must be 5.6 percent to achieve wafer‐to‐wafer temperature uniformity, while it should be 6.9 percent if the temperature of the secondary tube is considered to be the tube wall temperature.

Experiment results verify the effectiveness of the model. At the same time, the tube wall temperature is assumed to be influenced not only by the temperature of the silica tube but also by that of the secondary tube. The model predicts that the wafer temperature increased by 1°C if the tube wall temperature is increased as described in the foregoing. However, in the experiment, the wafer temperature increases by 1.6°C at most.
Photochemical vapor‐deposited silicon oxynitride films for solar cells
Authors: Shibata Noboru
Published: July 2007

Silicon oxynitride films (SiNXOY) were deposited at deposition temperatures between 100 and 300°C using mercury‐sensitized photochemical vapor deposition. The light source was a low‐pressure mercury lamp and the source gas was a mixture of NH3 gas and 5 percent SiH4 gas (95 percent N2 gas). The quality and interface property of these films were better than those of plasma‐CVD films. However, in the former films, the film quality was unstable and degraded rapidly with time when the deposition temperature was low.

Electron spectroscopy for chemical analysis (ESCA) indicated that the invasion of oxygen from air to the film caused a change in the film composition, resulting in the degradation of film property with time. The photochemical vapor deposition and plasma‐vapor deposition SiNXOY films were used as an antireflective coating for a single‐crystal‐Si solar cell; and it was found that using the former films, the short‐circuit current density and effective conversion efficiency were higher than by using the latter films. The difference in the foregoing results was believed to be due to the improvement of the interface property by photochemical deposition films.
Implementation of a class of asymmetrical neural networks with application to an a‐d converter
Authors: Sato Shigeo , Nishimura Toshihiko , Murota Junichi , Nakajima Koji , Sawada Yasuji
Published: July 2007

This paper attempts to clarify the problems which occur in implementation of a large‐scale neural network. First, a neural A‐D converter with CMOS circuits is designed. Asymmetrical synaptic weights were used to avoid the local minima problem for a neural A‐D converter. Furthermore, a chip is fabricated using 4 μm CMOS technology. Its successful action as an A‐D converter is verified and some possible causes of misoperation of the present circuit are presented.
Optical soliton transmission
Authors: Nakazawa Masataka
Published: July 2007

This paper discusses the basic properties and advantages of optical solitons which are under investigation in many countries for the purpose of their application in realizing ultrahigh‐speed communications. Especially, the recent developments in erbium optical amplifiers, which are epochal in optical soliton transmission, have made soliton communication actually realizable. Here, the techniques of the so‐called dynamic soliton communication are considered and recent research is reported.
Substrate‐voltage control circuits for DRAMs at power‐on timing
Authors: Miyamoto Hiroshi , Suwa Makoto , Tokami Kenji , Yamada Michihiro
Published: July 2007

This paper proposes two substrate voltage control circuits to prevent the latch‐up at power‐on of CMOS DRAM due to the substrate potential rise.

One of the circuits is a substrate voltage‐clamp type which clamps the substrate voltage to the ground during power‐on to prevent the substrate potential rise due to the capacitive coupling from then‐well.

The second circuit is a clamping circuit of memory cell‐plate voltage and bit‐line precharge voltage to the ground also at power‐on to prevent the substrate voltage rise due to the capacitive coupling from the memory cell plate and the bit line.

The clamping period of these circuits is determined by the power‐on reset signals generated inside the DRAM chip during power‐on. Furthermore, to effectively operate the clamping circuits by different timing for clamp release of each clamping circuit, two‐step power on reset signals is used. Adopting these circuits to an actual 4‐Mbit DRAM test device, the desirable operation of the circuits by clamping the substrate voltage, the memory cell plate voltage, and bit‐line precharge voltage to the ground during power‐on has been confirmed by waveform observation. Then the latch‐up prevention during power‐on is confirmed in the actual device.
US‐DMOS: A novel structure for power mosfets
Authors: Morikawa Masatoshi , Yoshida Isao , Kobayashi Masayoshi , Fukuda Takashi , Fujita Yuzuru
Published: July 2007

This paper describes a novel vertical power MOS‐FET with low on‐resistance and large avalanche current, called US‐DMOS (U‐grooved self‐aligned DMOS). It features a U‐grooved self‐aligned source and base contacts with respect to the gate electrode, which reduces the cell size to two‐thirds the conventional cell size and reduces the parasitic base resistance.

Using three‐dimensional simulation on this device structure, the reduction on the on‐resistance by the formation of the U‐groove and the increase of the avalanche current by the reduction of the base resistance were proved. In ann‐channel test device with a drain current of 60 V, the on‐resistance was 156 m Ωmm2, which is 30 percent lower than in a comparable device with a conventional structure. In addition, the avalanche current was one order of magnitude higher in this device.
Formulas for estimating the wide‐band reflection characteristics of inductive window with thickness in rectangular waveguide
Authors: Ishihara Fujiio , Sibazaki Toshihiko , Suga Takashi , Iiguchi Shinichi
Published: July 2007

The symmetric and nonsymmetric inductive windows in a rectangular waveguide are analyzed in a theoretically rigorous manner in which the window is treated not as a discontinuous but continuous structure and the normal mode expansion method (transmission line equation) is applied. The reflection coefficient including the phase is derived and a design chart applicable to windows with various dimensions is created. The analysis is carried out even for the cases in which the thickness of the plate cannot be neglected.

Next, experiments are carried out at × band. It is confirmed that the theoretical and experimental results agree well in a wide frequency range even for the case with a nonnegligible plate thickness. Further, an equation with a better approximation than the one in the conventional approximation equation is derived for convenience of the circuit designer.
Propagating beam analysis by alternating‐direction implicit finite‐difference method
Authors: Yamauchi Junji , Ando Takashi , Nakano Hisamatsu
Published: July 2007

The three‐dimensional beam propagation problem expressed by the Fresnel equation is analyzed by the beam‐propagation method using an alternating‐direction implicit finite‐difference method (ADI‐BPM). First, following the formulation of the finite‐difference method, the equations to be analyzed are rearranged. The fundamental and higher‐order mode propagation problems in a step index fiber are treated, and the accuracy and advantages of the ADI‐BPM are investigated. It is found that the computing time is shorter and the step length in the propagation direction can be made larger in the ADI‐BPM than in the beam‐propagation method based on the fast Fourier transform (FFT‐BPM).

As another advantage in the ADI‐BPM, the usefulness of the transparent boundary condition is described. It is shown that the spreading problem of a Gaussian beam can be analyzed without setting up the absorbing functions needed in the FFT‐BPM. Further, as an example to prove the effectiveness of the ADI‐BPM for the analysis of the problem in which the guided mode and the radiation mode are mixed, the transmission efficiency is evaluated in the case where an axial offset exists in the fiber junctions. The effect of the coherent coupling is studied.
Resonant frequency analysis of a dielectric ring resonator for a new method of moisture content measurements
Authors: Okamura Seichi , Sone Masahiro
Published: July 2007

It is proposed that the moisture content measurement for small and randomly shaped materials that was difficult by the conventional electrical methods be done by a new technique making use of the resonant frequency of a dielectric ring resonator. An analysis of the resonant frequency and a possibility of the new measurement method are discussed.

First, for taking the correlation of the moisture content with the shift of the resonant frequency of a moist sample within a resonator caused by the change of the permittivity, the theoretical value of the resonant frequency was derived by the mode matching method when an arbitrary dielectric sample was placed at the hollow central part of a dielectric ring.

A theoretical equation was derived and its validity was confirmed by comparison of the theoretical and experimental values for a known dielectric sample. From the relationship between the shift of the resonant frequency and the permittivity of the sample obtained from the theoretical equation, the shift of the resonant frequency is found usable for measurement of moisture content.

Further, this was confirmed by the measurement in the case where cardboard is used as a sample in a Teflon ring resonator. The measured and theoretical results for high moisture contents were compared. The discrepancy from the theoretical results is several percent. A possibility was demonstrated for a new moisture content measurement technique based on the shift of the resonant frequency of a dielectric ring resonator and the sample weight.
Effect of conductor losses in new‐structure filters for suppressing microwave leakage
Authors: Iwabuchi Koji , Kubota Tetsuo , Sugaya Yukitoshi , Kashiwa Tatsuya , Fukai Ichiro
Published: July 2007

As a waveguide‐type broadband elimination filter preventing leakage from a microwave heating system, a waffle‐iron type filter is known which consists of a periodic structure of a multiple post structure with many circular or rectangular cylindrical metal posts placed periodically inside a waveguide. The theoretical analysis of this filter has been limited to the case in which the conductor loss is neglected. Therefore, the attenuation at the resonant frequency of this filter becomes infinite in the computation and is significantly different from the practical situation.

To resolve this problem, the present paper derives theoretical equations including the conductor loss from the equivalent circuits for not only this filter but also the multiple‐slit type and the multiple rectangular‐plate type which are newly developed for mass production. The theoretical and experimental values are compared. It is confirmed that the frequency characteristics of the attenuation of the filter can be estimated theoretically including the resonant point.
Preparation and core loss of CoZrMo/polyimide stacked thin‐film core
Authors: Okuno Hikaru , Sakaki Yo
Published: July 2007

A stacked thin‐film core for large amplitude rf magnetization is fabricated. The soft magnetization characteristic and loss is measured and the application of the core is discussed by comparing it with other types of cores. The core is formed by depositing a 2‐μm thick CoZrMo film on a 12.5‐μm thick polyimide film using an opposing target sputtering system. When the target ratio of Co:Zr:Mo was 82.2 percent:5.7 percent:12.1 percent, the saturation magnetic flux density Bs was 0.32 T. Even without thermal treatment, a core with a small coercive force (Hc) = 4.8 A/m (0.06 Oe)) is obtained.

The hysteresis loss was close to that of a 5‐μm thick crystalline permalloy wound core but is one order of magnitude higher than that of amorphous (FeCoCr)75(SiB)25 thin‐film ribbon. This indicates that the core should be heat‐treated to improve the hysteresis property. When the maximum magnetic flux density Bm was 0.1 T at 10 MHz, the core loss was about 8 J/m3, which was close to that of 3.8‐μm thick amorphous (FeCoCr)75(SiB)25 thin‐film ribbon, which provides the lowest core loss.

When Bm = 0.02 T at 10 MHz, the core loss was one‐third that of the supermalloy wound core and one‐tenth that of MnZn ferrite. At 4 MHz, the loss was lower than that of a 5.3‐μm amorphous (FeCoCr)75(SiB)25 thin‐film ribbon. The frequency dependence of the core loss was less than that of other cores because the eddy current loss was low.

The proposed core can be applied for a high‐amplitude rf magnetization if the hysteresis loss is reduced.
An experimental study on the increasing phenomena of light intensity at the latter half of opening arc
Authors: Kubono Takayoshi , Okumura Takahiro
Published: July 2007

The time dependencies of the voltage, current, and the radiated light intensity of the opening arc discharge were investigated on butt‐type contacts where one end each of two silver columnar bars was fastened to a holder with large mass. Then electrical contacts were formed with the other end of the bar in the dc 10‐A resistive circuit.

It was found that the light intensity increases suddenly at the latter half of an arc duration if the 1‐mmϕ electrode is long. However, if the 1‐mmϕ electrode was exposed with air‐blow or if the electrode diameter was 5 mm, the sudden increase in the light intensity was not observed at the end of the opening arc duration.

When one end of a high‐temperature bar was heated further, the temperature gradient near the heated surface becomes smaller and the heat quantity flowing by thermal conduction is smaller. Therefore, the heated surface becomes further high temperature, thereby causing the acceleration of evaporation of the electrode material. We believe that at the latter half of a long opening arc duration, the number of atoms evaporated from the electrode increases, the number of ionized atoms increases, and then the light intensity increases suddenly.
Characteristics of an open‐boundary circular Čerenkov laser immersed in an infinite magnetostatic field
Authors: Horinouchi Katsuhiko , Hirakawa Isao , Shiozawa Toshiyuki
Published: July 2007

A theoretical discussion is given on the characteristics of an open‐boundary Čerenkov laser which is composed of a circular conducting cylinder coated with a dielectric sleeve and a hollow relativistic electron beam focused with infinite magnetostatic field, and the following results are obtained.

First, the growth rate decreases as the dielectric‐beam gap increases. Second, the frequency of the growing wave can be varied by varying the velocity of the electron beam. Third, compared with the case for a nonmagnetized beam, the growth rate decreases for an infinitely magnetized beam; but otherwise similar characteristics are obtained for both cases. Finally, as the ratio of the radius of a conducting cylinder to the thickness of a dielectric sleeve increases, the growth rate and frequency of the growing wave increase gradually and they tend to the characteristics for a planar laser for sufficiently large values of the ratio.
Surface‐emitting semiconductor lasers and surface‐operating functional devices
Authors: Iga Kenichi
Published: July 2007

Surface‐emitting semiconductor lasers have attracted attention because of their applications in new fields of optoelectronics such as parallel processing, optical interconnections, etc. In these lasers, light is emitted perpendicularly to the semiconductor substrate which creates the possibility of two‐dimensional parallel integration.

In this paper, the state of research on surfaceemitting semiconductor lasers is discussed first as are various structures of surface‐emitting semiconductor lasers with vertical, horizontal, and folded resonators. The formation of a buried structure or highly reflective configuration employed to achieve the low threshold operation of surface‐emitting semiconductor lasers with vertical cavities are focused upon and their oscillation characteristics of two‐dimensional array arrangements are introduced.

Finally, the recent progress of surface‐emitting lasers and surface‐operating functional devices together with their future prospects are presented.
A new method of optical coupling between waveguides and photodiodes using waveguide‐type layered optical couplers
Authors: Koike Shinji , Takahara Hideyuki , Katsura Kohsuke
Published: July 2007

In an attempt to develop a waveguide‐type layered optical coupler which has the same cross‐section dimension of dielectric layers as the optical waveguide, a new optical coupling system is discussed. This system is designed to couple the flip‐chip‐mounted photodiode with the waveguide. Because the proposed couplers can be manufactured in quantity, they have the potentiality for applying to optical interconnection modules where a large‐scale and a large number of optical connections are required.

The present paper discusses the performance of the waveguide‐type layered optical coupler based on the analysis by the beam propagation method (BPM) and on the experimental results. Both the power transfer from the waveguide to the coupler and the radiation process from the coupler to the photodiode are both clarified. These results indicate the optical coupling between the photodiode and the optical waveguide. Further, the optimum coupler‐structure for the maximum power transfer ratio from the waveguide to the coupler, which performance is least sensitive to the thickness error, is discussed. The coupling efficiency of 22 percent for the Gediode is obtained.
Analysis of an optoelectronic integrated functional device with positive optical feedback
Authors: Osawa Yasuhiro , Onodera Noriaki , Satoh Shiro
Published: July 2007

A fundamental and analytical model on optoelectronic integrated functional devices is discussed. In this model, the optoelectronic device with the positive feedback consists of the light emitter and the photodetector, which are electrically connected in series. The positive optical feedback is considered from the light emitter to the photodetector. A steady‐state solution is discussed for the optical functions of the device for various parameters. The light emitter is treated as the current‐light transducer, and the photodetector is modeled as the resistance which varies with the input‐light intensity. The parameters of voltage V, load resistance RL, light feedback ratio β, and conversion efficiency A are introduced. For those parameters, the condition for each optical function of the device is solved. The two cases for the detector characteristics are discussed and the distribution map of functions is obtained. Also, the parameter fitting is made to compare with the experimental results obtained for the hybrid structure and a reasonable agreement is achieved.
Propagation of nonlinear surface wave in linear‐nonlinear optical waveguide structure
Authors: Ohke Shigeaki , Umeda Tokuo , Cho Yoshio
Published: July 2007

In a nonlinear optical waveguide, it is not necessary to use a three‐layered structure as in the case of a linear optical waveguide. Even in a two‐layered structure of linear‐nonlinear configuration, there exists a stable light propagation mode along the interface. It is possible to study the structure by subdividing the nonlinear medium constituting one side of the two‐layer configuration.

This paper studies the behavior of the nonlinear surface propagation wave along the interface of the two‐layered linear‐nonlinear configuration by a numerical solution based on the multisegmentation method for the case where the optical intensity dependence of the nonlinear refractive index of the nonlinear region is positive. There also exists a stable light propagation mode in a linear‐nonlinear multilayered optical waveguide in which the nonlinear medium on one of the two regions is made of a multilayered configuration such as a multiple quantum well. It is shown that this linear‐nonlinear multilayered optical waveguide can be treated globally as a linear‐nonlinear two‐layered structure because the nonlinear multilayered region can be treated as a single‐layered nonlinear medium. Further, it is demonstrated that the behavior of the nonlinear surface wave in a nonlinearlinear‐nonlinear three‐layered structure can also be studied in a manner similar to that for the linear‐nonlinear two‐layered structure.
Surface potential control of electrostatic recording apparatus using a drum on which a photoconductor sheet is wrapped
Authors: Umeda Takao , Nakazawa Takasi , Miyasaka Tooru
Published: July 2007

This paper discusses the surface potential control of a high‐speed electrostatic recording apparatus using a drum wrapped with a photoconductor sheet. In the conventional surface potential control, the absolute value of the surface potential on the photoconductor is detected by a surface potential sensor to control the grid voltage. Therefore, in this method, the potential control is strongly dependent on the accuracy of the surface potential sensor and the sensor must be calibrated periodically.

In the method proposed herein, the surface potential of the sealing (cap) section where the photoconductor sheet is pulled out is set at the standard charge potential and the grid voltage is controlled by equalizing the surface potentials on the cap and the photoconductor.

After evaluating the application of our method to a high‐speed printer which is capable of printing at speeds over 100 pages/min, it was found that the surface potential on the photoconductor can be maintained at 700 ± 15 V.

Since the control method herein is a relative comparison method, the system performance is not influenced by the voltage drift caused by the toner adhered to the sensors. Therefore, the calibration of the surface potential sensor is not necessarily required. In addition, since relative output low‐cost surface potential sensors can be used, the control system can be cheaper.
Selective erasable and programmable NAND‐type MNOS memory
Authors: Sato Kazuo , Ueda Kenji , Kojima Makoto , Takata Takashi , Yokozawa Kenji , Morita Michio , Onishi Hideaki
Published: July 2007

This study was made of a new programming method and memory characteristics of an NAND‐type MNOS memory cell which uses half the size of the conventional two‐transistor structure using the same design rule. As a result, it was found that inadvertent writing can be prevented under the write inhibit mode by using a new sequencing (PURGE mode) which moves unnecessary thermal electrons generated under MNOS gate to the bit lines.

Also, it was verified that selective rewriting by NAND type can be realized. This prototype of NAND‐type MNOS memory cell can realize PURGE effect by applying 3 V and a very short pulse of 30 ns. It was found out also that possible number of PURGES of unselected memory cells at each writing is about 1010. The limit of the read cycle is about 106when the word line consists of 128 bytes.
Application of a liquid crystal microlens to an optical fiber switch
Authors: Nose Toshiaki , Sato Susumu
Published: July 2007

An optical fiber switch has been fabricated by combining an optical fiber and various liquid crystal microlenses prepared by using different liquid crystal materials and molecular orientation methods. By adopting various driving methods, the improvement in response and recovery characteristics has been attempted. In hybrid‐aligned liquid crystal microlens using a liquid crystal with positive (p‐type) dielectric anisotropy, good focusing characteristics can be obtained and a wide variability has been attained because there are no disclination lines which normally occur in the homogeneously aligned liquid crystal microlens. In hybrid‐aligned liquid crystal microlens using a liquid crystal with negative (n‐type) dielectric anisotropy, the improvement in focusing characteristics compared to the homeotropic molecular orientation has been attained because the polarization characteristics of incident light can be used effectively. It has also been clarified that the recovery characteristics are improved by the dual frequency driving method and that the response and recovery characteristics in the case of microlens with n‐type liquid crystal are both improved by the driving method with bias voltage application, which are also effective for the variable characteristics of the coupled light. Furthermore, these characteristic differences are discussed in terms of the liquid crystal molecular orientation state in the nonuniform electric field for each liquid crystal microlens.
An optoelectronic adaptive device and its learning performances
Authors: Kanamori Kohji , Tsuji Kiyotaka , Yonezu Hiroo , Pak Kangsa , Takano Yasushi
Published: July 2007

To realize a large‐scale and high‐speed neural network, an exclusive hardware is indispensable, as is a new concept on a circuit with an enormous number of interconnections among neurons. An important function in neurocomputing is self‐organization by learning. This self‐organization can be accomplished by the adaptive function of the synaptic connection in neurons, but no such devices have been realized. Based on the optoelectronic‐integrated circuit (OEIC) model with optical wiring using the parallelism of light, a new device/circuit has been designed and fabricated. This device has the adaptive function in which a synaptic connection weight Tij changes with an external pulse (teaching signal). The performance of the device which consists of fundamental networks based on back propagation (BP) was examined and compared with the simulation result. The basic adaptive function and self‐organization function were confirmed.
Vertical‐to‐surface transmission electrophotonic device and its application to optical interconnection
Authors: Yamanaka Yutaka , Numai Takahiro , Yoshihara Kazuhiro , Kosaka Hideo , Kurihara Kaori , Sugimoto Mitsunori , Kasahara Kenichi , Ogura Ichiro , Kubota Keiichi
Published: July 2007

In optical interconnection, the cascade optical interconnection using two‐dimensional optical switch devices is an important basic structure. To realize such an optical interconnection, the vertical‐to‐surface transmission electrophotonic device (VSTEP), which has a planar structure easy for two‐dimensional integration and is capable of light emission, light detection, and latching, has been developed.

Utilizing the optimized combination of a pnpn thyristor structure, double heterojunction structure and vertical cavity structure, efficient laser mode emission and switching characteristics were obtained.

In the optical interconnection using the differential structure, optical switching was achieved with optical energy as low as 150 fJ. An operating speed of 25 MHz was confirmed in the continuous mode. In addition, using the cascade characteristic in the device‐to‐device interconnection, the shift‐register operation was carried out using the optical interconnection between four optical array switches.
Amplitude‐stabilizing circuits for three‐phase ultralow‐frequency oscillator
Authors: Miyazaki Tomoyuki , Takeishi Taisuke
Published: July 2007

The rise time of the oscillation amplitude which is a problem in an ultralow‐frequency oscillator is discussed for a three‐phase CR oscillator. Four amplitude‐stabilizing circuits are proposed and their dynamic characteristics are compared by simulations. The computation was based on the Runge‐Kutta method. The analysis was applied to the three‐phase ultralow‐frequency switched‐capacitor oscillator to confirm the operation.

By means of the method for installing a positive feedback in each of the three‐phase shifters, a rise time of less than one‐tenth period was obtained. Analog multipliers were used for the control of the feedback voltage gain and the oscillation amplitude detection.
Effects of air pressure on transition boundary from metallic to gaseous phase in W break arc
Authors: Yoshida Kiyoshi , Takahashi Atsuo
Published: July 2007

To determine whether aW break arc continues only in the metallic phase until its extinction or its phase changes from the metallic phase to gaseous phase, the air pressure P was varied from 50 to 760 mmHg under the condition where the supply voltage E was 48 V, the load inductance L was 2.3 mH and the close contact current I was between 0.6 and 6 A.

The waveforms of arc with a phase other than the metallic phase were categorized as types I and II. In type I, the voltage increased rapidly in a stepped form and reached 30 to 40 V in low pressure. In type II, the gradient of the voltage increased varied. Type I occurred at a lower I0 than type II. In type I, I0 decreased with a decrease of P while in type II I0 increased with a decrease of P. When I0 was close to the threshold value of type II, the metallic phase duration tm increased suddenly.

The contact gap corresponding to the sudden increase in the metallic phase duration agreed with the minimum point of Paschen's spark discharge curve under a given pressure.
A velocity‐matched guided‐wave optical modulator using an inverted slot line
Authors: Yoneyama Tsukasa , Niinuma Keiichi , Kanno Seiji
Published: July 2007

With the purpose of developing a highly efficient guided‐wave optical modulator, an inverted slot line has been proposed for realizing a perfect velocity matching. Modulation experiments were conducted at the 10‐GHz band. Despite its simple structure, the inverted slot line can increase the phase velocity of the modulating wave substantially by changing the spacing between the slot surface and the ground plane, and hence the velocity matching can easily be attained. From the structural limitation of the inverted slot line, the input of the modulating wave from a coaxial cable must rely on the non‐contact excitation.

A transition for such a purpose was fabricated first. Next, the propagation characteristics of the inverted slot line were investigated experimentally. It was confirmed that perfect velocity matching can be realized between the optical wave and the modulating wave if the spacing between the slot surface and the ground plane is about 200 μm for 10 GHz and 22 μm for 50 GHz, although certain variations exist, depending on the slot width. An optical modulator was actually built with a Ti:LiNbO3 optical waveguide, and the phase modulation operation was confirmed at a wavelength of 633 nm. At the modulating frequency of 9 to 12 GHz, the maximum phase modulation of 2.11 rad was measured with a modulating power of 100 mW. Hence, the possibility of a highly efficient guided‐wave optical modulator was demonstrated.
Finite‐element analysis of open‐type axially symmetric waveguides
Authors: Ohkubo Fuminori , Maruta Akihiro , Matsuhara Masanori
Published: July 2007

A new method is proposed for the numerical analysis of the propagation characteristics of open‐type axially symmetric waveguides by means of the finite element method.

First, a novel variational expression suitable for the waveguide analysis is presented which uses electric field components as the trial function. When this variational expression is used in the finite element analysis, no spurious solution is generated.

Next, a mapping technique is proposed to apply the finite element method to the entire region of the opentype axially symmetric waveguide. In this method, the entire region of the open‐type axially symmetric waveguide is divided into a finite core region and an infinite cladding region. By means of a coordinate transformation, the cladding region is mapped to a finite region. The finite element method is applied to the finite core and mapped cladding regions and the variational expression is reduced to a generalized eigenvalue problem in which the propagation constant is the eigenvalue. Hence, no repetitive calculation is necessary and the computational effort can be reduced.

As practical examples, a step index fiber and a graded index fiber are analyzed numerically and the validity of the proposed method is confirmed.
LiNbO3 waveguide SHG devices based on a ferroelectric domain‐inverted grating induced by SiO2cladding
Authors: Fujimura Masatoshi , Suhara Toshiaki , Nishihara Hiroshi
Published: July 2007

LiNbO3 waveguide quasi‐phase matching (QPM) second‐harmonic generation (SHG) device is promising as a short‐wavelength coherent light source. To realize such device it is important to establish a ferroelectricdomain inversion technique. The authors have found that by heating an LiNbO3 crystal for two hours at 1000°C with SiO2 cladding of about 0.1 μm thick on the +Z surface, the domain inversion is induced under the cladding. This inversion method is suitable for device fabrication since uniform domain inversion is induced with good reproducibility under a wide heat‐treatment condition. The dependence of the SHG efficiency on the waveguide size and on the domain inversion cross‐section structure is calculated.

A prototype waveguide SHG device, which can compensate for the residual phase mismatch, with domain‐inverted grating formed by this inversion method was demonstrated. An SHG experiment using a CW‐Nd:YAG laser light as the fundamental wave resulted in a high SHG efficiency of about 45‐percent W. It was seen that the domain‐inverted grating formed by the present method is suitable for application to QPM‐SHG devices.
Hybrid‐type optical bistability in a thin‐film polymer waveguide doped with nonlinear organic dyes
Authors: Muto Shinzo , Miyagawa Koichi , Ozawa Toshio , Sugiyama Shigeru
Published: July 2007

It is demonstrated theoretically and experimentally that hybrid‐type bistability operations based on the Kerr effect can be obtained in a Mach‐Zehnder interferometer‐type thin‐film optical waveguide made of a polymer thin film doped with nonlinear organic dyes such as disperse orange 3, trans‐β‐carotene and nitroaniline derivatives. It is shown also that the Kerr constants of the dye‐doped polymer thin film can be measured by using the optical control characteristics in this device. The values are 10−14 to 10−13 m/V2 even with dye‐doping of several wt%. Further, an optical‐optical switching operation is possible although a high feedback gain is required.
A parallel divider for architecture numbers of arbitrary word length
Authors: Nakamura Tsugio , Kasahara Hiroshi
Published: July 2007

The high‐speed and highly accurate arithmetic unit is becoming more important. Especially, one factor that determines the system performance is the execution of the multiplication/division, which arises frequently and takes a long computation time. The most appropriate idea in improving the speed is the parallel hardware architecture.

Often in the system design, the capacity of the initially designed arithmetic unit becomes insufficient due to the change of specification and the upgrading of the system function after the design making the circuit redesign necessary. Especially, in the case of the divider, such a system redesign is not easy since it cannot be used if the number exceeds the word length. If the number exceeds the operational capacity even by a bit in the divider, it is difficult to cope with the requirement, even if a memory or an external circuit is added. Hence, there is less advantage in fabricating a dedicated integrated circuit (IC) and there are only a few examples of the one‐chip divider.

The high‐speed dedicated arithmetic unit includes digital signal processing (DSP) circuitry and a DSP coprocessor, but the division is executed by the software since it is not advantageous to include the divider. This requires a long computation time.

From such a viewpoint, this paper proposes an architecture for the parallel divider which can cope with any requirement for the accuracy only by employing several similar dividers. Detailed problems in the expansion of the operational accuracy are discussed, and the proposed divider architecture is described. The one‐chip implementation also is discussed.

By this structure, an advantage is produced to prepare the dedicated divider, and the cheap, efficient and high‐speed division can be realized by a relatively small‐scale divider. The proposed divider will be applied widely, not only to the general scientific computations but also to various control systems, signal processing, and computer communication.