bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic field modulation recording with multipulse laser irradiation on magnetooptical disk drive
Authors: Kawasaki Satoshi , Sohmuta Mitoshi
Published: July 2007

A magnetooptical disk driver which adopts the magnetic field modulation recording scheme has been developed for filing data. to apply the magnetic field modulation magnetooptical file system, such as a minidisk, to personal computers, essential technology must be developed. A noncontact magnetic head type and active spacing system were adopted to achieve high reliability and accessibility.

To avoid system disturbance due to the weight increase in the head, linear motors were used to achieve independent motion of the optical head and magnetic head. A sputter‐etching treated magnetooptical disk was developed as the magnetic field modulation medium for low‐field recording. to cope with low‐field noise during magnetic field modulation recording, multipulse laser irradiation was used. In this method, the magnetized segment had a sharp edge even when the magnetic field was weak, resulting in a reduction of jitter in the playback of the signal.

Using the foregoing technologies, a test driver for recording and playback using the compact disk (CD) format was evaluated. In the test, the jitter value was less than 20 ns and the block error rate was on the order of 10−4.
Four‐wavelength DBR laser array using selective MOCVD growth
Authors: Katoh Yukio , Kunii Tatsuo , Matsui Yasuhiro , Wada Hiroshi , Kamijoh Takeshi , Kawai Yoshio
Published: July 2007

A four‐wavelength DBR laser array, fabricated using selective metalorganic vapor‐phase epitaxy (MOCVD) growth, has been developed as a light source for a wavelength division multiplexing (WDM) system. Four different lasing wavelengths were obtained by varying the thickness of the waveguide. This enabled fabrication of lasers having different wavelengths but gratings with the same pitch.

First, the InGaAsP layer grown on an InP substrate which was patterned with stripes of different widths by using an SiO2 mask is evaluated. the growth rate of the InGaAsP layer between SiO2 masks could be varied to twice as fast as in a flat area while maintaining good quality of the crystal. Next, a four‐wavelength DBR laser array is fabricated by using selective MOCVD growth and a grating with the same pitch. the lasing wavelength was controlled at 5‐nm intervals over a 15‐nm range.
Design of very low‐distortion, four‐quadrant analog multiplier‐type CMOS‐OTA considering variation of mobility according to the gate voltage
Authors: Igarashi Yutaka , Hyogo Akira , Sekine Keitaro
Published: July 2007

This paper discusses the four‐quadrant multiplier‐type operational transconductance amplifier (FQAMTOTA). the basic principle of its operation is described. the circuit uses four MOSFETs (MRA) operating in the resistor region as well as the identical voltage level‐shift circuit (IVLS). Although it has a simple structure, its feature is that it has a wide linear input range and the transconductance can be controlled for both signs. For the FQAMT‐OTA to operate at a high‐frequency signal range, MOSFET with a short channel must be used as MRA.

In most of the past designs of CMOS circuits, the effective carrier mobility μ is assumed as constant. In practice, however, μ has the property that it depends on the gate‐source voltage. This effect cannot be ignored when the circuit is designed using MOSFET with a short channel because it can cause a large second‐order harmonic distortion in the output of FQAMT‐OTA. Another point is that the power consumption increases when MOSFET with a short channel is used. the idea in this paper is that those problems can be remedied only by using the bootstrap circuit as MRA. A construction of the improved FQAMT‐OTA is shown together with the result of simulation using PSpice.
Integrated master slice‐type transimpedance amplifier photosensors using pin‐bipolar process
Authors: Kyomasu Mikio
Published: July 2007

Master slice‐type transimpedance (TZ) amplifier sensors based on the pin‐bipolar process are developed which have applications in optical communications, computer LAN, rangefinding apparatus, and optoelectric switches (optoelectronic SW). the pin‐bipolar process is used in these devices and the pin photodiodes, together with the detector current amplification circuitry, are monolithically integrated by master slicing on the substrate. It became possible to alter the photodiode area of octagon of 0.5 mmϕ, that of 0.8 mmϕ, or □ of 1.0 mm2by changing only the aluminum interconnections. Further, the photodiodes are separated by dielectric isolation andp+diffusion, which enabled the achievement of low crosstalk and successful design of receivers matched to the characteristics of the TZ amplifier. In the integrated circuit area, the wideband amplifier, the inverter, and the wideband differential amplifier are included, to which the specific capacitance prepared by the pin‐bipolar process is added. These allowed design of master slice‐type integrated optical sensors by changing only the aluminum interconnections and contact mask of each TZ amplifier. the chip size of the achieved device, sealed in the TO‐18 package suitable for uses as integrated TZ amplifier sensors, is 1.7 × 1.7 mm2□.

From the evaluation results of the designed device, the cutoff/frequency was found to be about 150 MHz with the minimum sensitivity of 1.3 mV/nW and allowable external light intensity of 30μW. These results show that the master sliced TZ amplifier can satisfactorily respond as an integrated optical sensor.

In other applications, it is indispensable to overcome the problem of master slice realization of arbitrary shape photodiodes. In this respect, the isolation technique developed here is believed to be an attempt in their realization.
Cl2‐ECR plasma etching of III/V semiconductors and its application to photonic devices
Authors: Yoshikawa Takashi , Kohmoto Shigeru , Sugimoto Yoshimasa , Asakawa Kiyoshi
Published: July 2007

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

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

Low‐power monolithic quadrature modulators for digital mobile communication have been realized for 800‐MHz and 140‐MHz bands. Considering the application to ultrasmall portable telephones, the design reduces the power consumption drastically and realizes a complete one‐chip configuration with no adjustments or external parts. For this purpose, several proposals are made for the circuit configuration.

First, a total configuration using a constant phasedifference‐type 90° combiner is proposed to reduce the circuit size and chip area dramatically and to eliminate the phase adjustments. Next, for a double balance mixer (DBM) which is the key for modulation characteristics, an analog‐switch‐type DBM is used for the 800‐MHz band and realizes a highly accurate modulation wave without the influence of device variation due to the semiconductor fabrication process. Furthermore, a bootstraptype buffer amplifier with high current utilization has been devised for the output stage.

The fabricated 800‐MHz band (GaAs) and 140‐MHz band (Si) quadrature modulator integrated circuits (ICs) have shown superior performance as π/4 shift QPSK modulators. the power consumption is 65 mW and 32.5 mW, respectively, realizing a dramatically low power compared to conventional methods.
Volume integral equation for analysis of quantum electron waveguide circuits
Authors: Tanaka Kazuo , Yoshino Yoshikatsu , Ootera Hiroki
Published: July 2007

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

With a view to make the finite‐element analysis of anisotropic graded‐index channel waveguides efficient, quadratic triangular elements are used. In addition, an application of the numerical integration formula by Hammer et al. is attempted for the integration calculation necessary for formation of the element matrix. Numerical investigation has been carried out for a Ti‐diffused LiNbO3 waveguide. It is confirmed that highly accurate solutions can be obtained with small‐scale computation in the present method.

Also, it is found that, if the past is still used, significant defference appears in not only the phase constant of the guided mode but also in the coupling length of the optical directional coupler indispensable for configuration of the optical integrated circuit, compared with the results considering the anisotropy. Further, the validity of the results by the scalar finite element method is confirmed by comparison with the results by the vector finite difference method.
Temperature‐compensated crystal oscillator using a two‐port crystal resonator
Authors: Ueno Yoshifusa
Published: July 2007

In general, the oscillation frequency of a quartz crystal oscillator is shifted by varying the load capacitance of the quartz crystal resonator. Since the relation between load capacitance and oscillation frequency of the crystal resonator is nonlinear, the rate of change of frequency is slightly different from the load capacitance before and after the frequency shift. When the variation of oscillation frequency due to aging is compensated using the temperature‐compensated crystal oscillator (TCXO) or the voltage‐controlled temperature‐compensated crystal oscillator (VCTCXO) or the oscillation frequency is shifted, the frequency compensation amount set by the temperature compensation circuit is different before and after the compensation. Thus, the frequency versus temperature characteristics vary.

To solve this problem, the author has developed a special quartz crystal resonator with two‐port electrodes. Since this crystal resonator has two load capacitances, the compensation of the temperature characteristics and the shift of oscillation frequency can be conducted independently. Thus, the problem of the changes in the temperature characteristics due to the oscillation frequency shift of a TCXO has been solved. This problem could not be solved using the conventional quartz crystal oscillator having only one capacitance.

In this paper, measurement is made under the condition that the oscillation frequency of the TCXO using a two‐port crystal resonator is shifted by ± 15 ppm and the performance is compared with that of TCXO using a conventional crystal resonator. the measurement has revealed that the change of frequency versus temperature characteristics is extremely small when the oscillation frequency of the TCXO using a two‐port crystal resonator is shifted.
Alteration of the electrical properties of anodized silicon/crystal silicon sample by water vapor
Authors: Motohashi Akira
Published: July 2007

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

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

Composite materials of solid lubricants such as graphite, MoS2, WS2, etc., and metals are used as electric sliding contacts. However, few reports on the detailed characteristics of these composite materials have been made so far.

In this paper, to satisfy the broad market requirements and, in addition to the Cu‐Nb system reported previously, four newly developed and new commercialized types of Cu‐Sn system materials are investigated. As a result, it was found that the composite material Cu‐Nb system is superior to the Cu‐Sn system and it is clarified that both contact resistance and the coefficient of friction could be made lower in composite materials containing exclusively WS2 and free of MoS2.
Fundamental characteristics for ground‐resistance reducing material using water‐absorbent polymer
Authors: Yamane Hiroshi , Ideguchi Tsuyoshi , Tokuda Masamitsu , Koga Hiroaki
Published: July 2007

As the number of communication facilities increases, the number of grounding points needed for the facilities increases. In the high ground‐resistance areas with soils composed of volcanic ash or sand, it is difficult to achieve the specified ground resistance and, hence, a ground resistance‐reducing material must be used.

This paper proposes a method to reduce ground resistance using water‐absorbent material. Also, a method is described for measuring ground resistance using a box‐type metal container, where the influences from the walls and the bottom of the metal container are taken into account.

The properties of the ground resistance‐reducing material based on the water‐absorbent material which was solidified by using epoxy resin has been investigated to find the condition where the ground resistance was lower than when a grounding electrode was used and the compressive strength of the material was higher than that of bentonite. As a result, it was found that, when the water‐absorbing ratio was 1:2, the ratio of the weight of the water‐absorbent material to that of epoxy resin should be between 0.3 and 1.7.

It was found also that this ground‐reducing material was as effective as a grounding electrode with respect to the buried depth and earth conductivity and that the ground resistance decreased exponentially with a buried radius (αr−0.37).
Design and characterization of traveling wave optical modulators of LiNbO3 thin film waveguides grown by liquid phase epitaxy
Authors: Ohno Kazushige , Kouyama Tatsuya , Tsuji Masahiro , Nakamura Masanori , Izutsu Masayuki
Published: July 2007

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

This paper investigates the LiNbO3 waveguide etalon array which can be used as an optical frequency scale for the frequency standard for stabilization of a laser diode and the filter in the optical frequency domain. In a hybrid configuration made of cascaded fused quartz‐type branch guides, the resonant characteristics are evaluated. an etalon array filter characteristic with good waveguide uniformity is confirmed. Also, the stability of the fluctuation of each resonant peak frequency of the etalon array is evaluated with a frequency standard laser. In addition, a method is proposed for stabilization with a reference laser and an actual operation is confirmed. As a result, the frequency fluctuation of about 20 MHz with only the temperature control of 1/100°C is reduced to ± 2 MHz (corresponding to 1/1000°C) with stabilization by a reference laser. Further, an application example was presented when the present etalon array is used as a frequency substandard.
Twenty‐five‐inch diagonal high‐contrast color plasma display panels
Authors: Fujii Kozo , Sawai Hideo , Takano Yoshimichi , Sakai Tetsuo
Published: July 2007

A 25‐inch diagonal high‐contrast color plasma display panel was fabricated by using thick‐film printing technology. This paper discusses the design and process requirements for making this large‐size plasma display panel.

In designing the panel, priming paths were made in the gaps between cathodes and leveling barriers. This resulted in satisfactory discharge characteristics over the entire area of the panel. For the printing process, an improved printer and optimized printing conditions were used. the durability of the print screen was examined under the printing conditions.

To identify the cause of uneven luminance within the panel, the authors examined the effects of the distri bution of various parameters on the intenial surface of the panel and found that the precision of the positioning of cell formation elements is the most important factor in prevention of unevenness of luminance.
Design and simulation of optical integrated circuits
Authors: Koshiba Masanori
Published: July 2007

This paper describes the basic items needed for design and simulation of optical integrated circuits and analysis tools for optical waveguides. Because the finite element method and beam propagation method are emphasized, the scalar wave approximation (which has been extensively used) is used in the discussion. In addition, using examples of analyses on various optical integrated circuits, the design and simulation technologies for optical integrated circuits will be introduced.
A quasiphase‐matched waveguide for the blue second‐harmonic generation
Authors: Yamada Masahiro , Nada Naoji , Yamaguchi Takeshi , Saitoh Masaki , Watanabes Kenjiro
Published: July 2007

An optical waveguide second‐harmonic genration (SHG) device in a quasiphase matched (QPM) system that obtains blue laser light from an infrared laser diode has shown promise. to obtain sufficient output power, it is necessary to understand how a high‐frequency conversion efficiency is attained in the SHG device. the technology for periodic inversion of the sign of the nonlinear optical constant is the key to full development of the QPM system. Most of the nonlinear optical crystals used for optical waveguide SHG devices in the QPM system are ferroelectric. In such crystals, self‐generated polarization is inverted so that the inversion of the sign of the nonlinear optical constant is carried out by polarization inversion. the authors have succeeded in forming a periodic inversion mechanism extremely ideal to the QPM by applying an external electric field in the device using lithium niobate. A conversion efficiency reaching 600 percent/W · cm2 has been realized.

Various polarization inversion methods are introduced herein. the QPM system optical waveguide SHG device is explained in which the polarization periodic inversion mechanism is formed by the applied electric field on the lithium niobate.
Lossless and low crosstalk 4 × 4 optical switch array
Authors: Kirihara Toshio , Ogawa Mari , Inoue Hiroaki , Ishida Koji
Published: July 2007

The optical switch array is a key device for realizing photonic switching systems. A lossless and low crosstalk switch is the most desirable component of large‐scale switching systems which have more than 100 input/output ports. to realize such a switch monolithically, a carrier‐injection‐type optical single‐slip structure (S3) switch with traveling‐wave amplifier (COSTA) have been proposed. to realize the COSTA, a carrier‐injection‐type optical switch and an optical amplifier that are suitable for integration have been developed. First, a carrier‐injection‐type optical switch where the PN junction was formed by crystal growth was fabricated. It was confirmed that the characteristics of the device do not deteriorate during heating, which makes it suitable for integration. Next, the structure of an optical amplifier which can be integrated into the optical waveguide using the reactive ion etching (RIE) process was investigated. an optical amplifier that was integrated into a straight optical waveguide was fabricated, and it was confirmed that this amplifier could produce enough gain (internal gain of 25 dB) to compensate for the loss in the optical switch. Using these two basic techniques, a 4 × 4 COSTA was fabricated. With this 4 × 4 COSTA, fiber‐to‐fiber lossless (maximum gain of 5 dB) and extremely low crosstalk characteristics (ON‐OFF ratio of 54 dB) were demonstrated.
Semiconductor photonic integrated devices
Authors: Tada Kunio , Nakano Yoshiaki
Published: July 2007

Semiconductor materials are suitable for monolithic photonic integrated circuits since they can realize almost all the necessary photonic functions such as light emission, light amplifications, light detection, light modulation/switching and optical waveguiding. Additionally, since the figure of merit of various physical effects used to realize the foregoing functions is large and since it is easy to arrange the spatial region to generate these effects into compact and convenient shape, it is advantageous for small size and high performance.

The research and development of photonic integrated circuits utilizing semiconductors has an accumulation of history, knowledge, and technology, already spanning a quarter of a century. Although it has required a longer time before it becomes practical than the electronic integrated circuits, it has shown rapid progress since the end of 1980's. This is attributed to the combination of the driving force from the needs point of view based on the advances in semiconductor laser technology, introduction, and spreading of quantum well structures and evolution of processing technology such as epitaxial growth methods and the strong demand from the needs point of view toward all optical telecommunication networks where not only trunk lines but also switching nodes and subscriber lines use an optical wave.

This paper reviews the present status of photonic devices and circuits obtained by monolithic integration of semiconductor element devices by classifying them into light emitters, optical switches, and combiners/splitters. Finally, the necessity of semiconductor integrated photonic systems is set forth toward the future.
Reproduction of optical reflection‐intensity‐distribution using multimode laser coherence
Authors: Tanno Naohiro , Ichimura Tsutomu
Published: July 2007

A new reflectometry method is proposed which enables measurements of light‐reflection‐distributions with spatial resolutions below tens of micrometers. the method can be applied to the detection of the damaged point of optical fibers, optical integrated circuits (ICs), reproduction of optical waveguide three‐dimensional memories, etc. By consideration of the coherency of a multimode laser, it becomes possible to construct the reflectometer without the need for frequency scanning of the optical source and movable parts.

The interference light from the Michelson interferometer or from the interfaces of the multilayer object are analyzed (by the spectrometer) and square detected to obtain the interferospectrum of the interference light. Using the property that the interferospectrum is the duplicate of the reflection distribution, the Fourier inverse transform of the reflection distribution is carried out and the “spatialgram” is reproduced. the spatial resolution is determined by the inverse of the spectrumwidth of all modes. Therefore, even if a common multimode laser diode, available on the market with all‐mode spectrum‐width of 10 nm is used, the high resolution of about 34 μm can easily be achieved. Numerical results of the theoretical analysis of reflections, in the frequency domain, also are presented.
Analysis of dielectric optical waveguides using the nonorthogonal finite‐difference time‐domain (FD‐TD) method
Authors: Araki Makoto , Kashiwa Tatsuya , Tagashira Hiroaki
Published: July 2007

Research and development of optical circuit elements become important as the degree of integration of the optical circuit is advanced. Since the optical devices are integrated and become more complex and as optical circuit elements with high index difference begin to appear, the conditions of the weakly guided wave and of the reflectionless wave no longer hold rigorously. Hence, rigorous numerical analysis is needed.

One of the analysis methods for the optical circuit elements is the finite‐difference time‐domain (FD‐TD) method. Recently, as a generalization of the FD‐TD method, the nonorthogonal FD‐TD method has been proposed. In this paper, the optical circuit elements are analyzed by means of the nonorthogonal FD‐TD method which is capable of analyzing optical circuit devices with various shapes. First, tapered waveguides are analyzed. the results are compared with those by the beam propagation method (BPM) and the characteristics with respect to the tapered angle are derived. Next, a directional coupler with a high refractive index difference is analyzed. the effectiveness of the present method for the coupling characteristics is presented.
A thermal characteristic stabilization method for an optical voltage sensor using optical rotary power
Authors: Ohtsuka Masao , Furuta Takashi , Shimomura Teruo
Published: July 2007

The longitudinal type optical voltage sensor made of Bi12GeO20 (BGO) crystal is often used in practical applications because it has a large electrooptical coefficient γ41, temperature stability, and no natural birefringence. Since this electrooptic crystal has large optical rotary power, sensitivity degrades when the crystal is thick. However, if optical rotary power is utilized, it is possible to control arbitrarily the temperature coefficient × of the sensor sensitivity. It was proved theoretically that the temperature coefficient of sensor sensitivity was dependent on the temperature coefficient β of the half wavelength voltage Vπ, the temperature coefficient β of the optical rotary angle θ0 the crystal thickness d (optical rotary angle θ0), and the cut angle θ. In addition, in order to verify the theory, × was determined by evaluating a sensor at temperatures ranging from ‐20 to 80°C. As a result, it was found that the value of × varied arbitrarily from ‐7.6 × 10−4 to + 4.0 × 10−3 (1/°C).
Analysis of optimum behavior for peltier cooling system
Authors: Ogawa Yoshihiko
Published: July 2007

The optimum operating condition of a Peltier cooling system was accurately derived by using a thermoelectric differential equation developed by the author. Using the obtained result, the influences of the Peltier device current and length on the cooling characteristic were analyzed. One of the most serious drawbacks of the Peltier cooling system is the low value of COP; an increase of COP is the most important issue in designing a cooling system. the optimum operating condition described herein is that operation limit which provides maximum COP. When a large temperature difference is required, multiple stages of Peltier devices connected in cascade are used. Therefore, theoretical analysis for cascade structure used arbitrary N stages.
Uniform microdroplet formation of polymer‐dispersed liquid crystal using undercoating films
Authors: Fujikake Hideo , Takizawa Kuniharu , Kikuchi Hiroshi , Fujii Takanori , Kawakita Masahiro
Published: July 2007

It is found that liquid crystal microdroplets become uniform and their sizes are reduced if the substrates are coated with some undercoating film before forming polymer‐dispersed liquid crystal using the photopolymerization‐induced phase separation method.

In this study, polyvinylalcohol was used for the undercoating film because it has good wetting property to the liquid‐crystal material, resulting in suppression of nonuniform nucleation and growth of the microdroplets. In the polymer‐dispersed liquid crystal formed under ultraviolet (UV) irradiation with 10 mW/om2, the diameter of the liquid‐crystal droplets varied in a range up to approximately 6 μm without using an undercoating film while the variation of the droplet diameters became less than 2 μm when the undercoating film was used. As a result, the threshold characteristic in the electrooptic property, response time, spatial resolution, and film uniformity were improved drastically by using the undercoating film. By using the polymer‐dispersed liquid crystal formed in this new method, a high limiting resolution (as high as 128 1p/mm) was achieved. the polymer‐dispersed liquid crystal formed in this way is expected to be used for projection displays with high resolution and high brightness.
The oxidation process and dissipation factor of Al/Ta/Hf multilayered anodized thin‐film capacitors
Authors: Dobashi Tsuyoshi , Umezawa Toshiji , Sasaki Katsutaka , Noya Atsushi
Published: July 2007

It is known that the anodic oxidation of Hf proceeds by the diffusion of anions into Hf thin film and is affected by the other overlayered films existing on Hf in multilayered anodized thin‐film capacitors. to characterize multilayered thin oxide film structures necessary for the fabrication of high‐quality capacitors, a correlation between dissipation factor and oxidation process has been investigated as a function of anodization voltage and thinfilm thicknesses of Al/Ta/Hf and Ta/Al/Hf multilayers.

The results indicate that thin‐film capacitors with low dissipation factor can be obtained by anodizing Al/Ta/Hf thin films so long as their original multilayered structures are maintained during anodization and the Ta intermediate layer acts as a transport medium of oxygen ions for the bottom Hf layer. With increasing anodization voltage, Ta ions migrate toward the surface of the multilayer, which alters the original multilayered structure and contributes to higher dissipation factor.

When the intermediate layer is Al such as in the case of Ta/Al/Hf multilayer capacitors, the flow of oxygen ions to the bottom Hf layer is restricted during anodization by the formation of an oxidized Al layer and this makes the dissipation factor higher. It has been concluded that in order to fabricate thin‐film capacitors with low dissipation factor, it is vital to have the presence of an intermediate layer such as Ta which has a lower heat of formation for oxidation than Hf.
Densely spaced optical FDM‐homodyne detection systems using optical fitters
Authors: Yonenaga Kazushige , Norimatsu Seiji
Published: July 2007

This paper investigates the effect of channel‐to‐channel interference in optical frequency division multiplexing (FDM)‐homodyne detection systems that use optical filters for densely‐spaced optical FDM systems. Power penalties at BER = 10−9 for double‐sideband (DSB), single‐sideband (SSB), and vestigial‐sideband (VSB) signals were evaluated by approximating the channel‐to‐channel interference as Gaussian noise. the authors investigated four cases: where no optical filter was used; where an optical channel selection filter was used at the receiver, where an optical filter suppressing spectrum broadening was used for each channel before multiplexing at the transmitter; and where both of these filters were used. It has been shown that using an optical filter before multiplexing is effective for reducing channel spacing. the optical filterings are effective especially for SSB and VSB signals. Extremely densely‐spaced multiplexing with a channel spacing of less than twice the bit rate can be achieved with a power penalty of less than 0.1 dB.
Analysis of current runaway in a DC‐DC converter with current‐injected control
Authors: Matsuo Hirofumi , Kurokawa Fujio , Imamura Ken , Asano Mutsuyoshi , Koga Takashi
Published: July 2007

The purpose of this paper is to examine the occurrence mechanism of the current runaway phenomenon in the overcurrent limited mode of the dc‐dc converter with current injected control. Taking into account the time delay in the turn‐off instant of the switch, which is due to the dead time and the time constant of the control circuit and the dead time of the switch, this phenomenon is analyzed.

As a result, it is clarified that there exist two operation modes in the overcurrent limited mode of the dc‐dc converter with current‐injected control; in one mode, the current limiting characteristics are affected by only the dead time of the control circuit and the switch and, in the other one, both the dead time and the time constant of the control circuit and the dead time of the switch have an effect. the current runaway phenomenon occurs in the latter mode. the boundary condition of these two modes is defined. Consequently, the design criterion is presented to prevent the current runaway phenomenon.
Stability against temperature and environment for ground‐resistance reducing material using water‐absorbent polymer
Authors: Yamane Hiroshi , Ideguchi Tsuyoshi , Tokuda Masamitsu
Published: July 2007

As the number of communication facilities increases, the number of groundings installed in such stations also increases. It is difficult to achieve the specified ground‐resistance value in such high ground‐resistance regions as volcanic ashes, sands, and rocks. In this paper, as a ground‐resistance reducing material, a waterabsorbent material solidified by plastic hardener is treated. Its stability in an air and water environment is described.

As a water‐absorbing material, anhydrous maleic acid polymers are selected. It is found that this material maintains the characteristics for about 10 years if the performance degradation of 20 percent is allowed and about 20 years if 50 percent is allowed. For the reducing material made of an absorbing material solidified by epoxy, it is found from the environmental degradation characteristics by changing the temperature in air that the dry condition can be allowed for about one year during which the ground resistance can maintain its initial value if rain falls and is sufficiently stable. Further, from the environmental degradation characteristics in water, it is found that the ground resistance maintains the initial value and the compression strength is not degraded unless the temperature is more than 70°C. Hence, the stability is sufficient even in water.
Optical neurochip for image processing
Authors: Nitta Yoshikazu , Ohta Jun , Tai Shuichi , Kyuma Kazuo
Published: July 2007

This paper proposes a method to realize a highspeed processing of image data utilizing the analog memory function of the optical neurochip. The result of experiment also is presented. The features of the proposed method are that the image data can directly be processed in the two‐dimensional form and a large‐scale problem can be processed with a high speed by utilizing the spatial parallelism of the light.

In this paper, it is shown first that the variable sensitivity photodetector, which is the basic element of the system, can function as the optical analog memory, where the value proportional to the product of the input light intensity and the control voltage is stored hi the element as the light detection sensitivity and the stored value can be read by the optical signal. Then the application of the optical analog memory function to the image processing is considered. The optical neurochip is constructed by integrating the variable sensitivity photo‐detector in a two‐dimensional array, and it is shown that the difference of two input images can be calculated. The function is realized by selecting the polarity of the control voltage in inputting the pattern.

Lastly, the image difference function is applied in the experiment for the selective detection of the moving object where the dynamic image is used as the input. In other words, the light irradiated from the moving object is used as the input pattern; and it is shown experimentally that the trajectory of the moving object is detected but the signal is not detected when the object is still.
Vertical photonics: A new way to integrate photonic devices into optical fibers
Authors: Kawakami Shojiro , Hanaizumi Osamu
Published: July 2007

Vertical photonics is the technique of direct integration of optical functional devices or their integration into optical fibers. In optical fiber systems, it is usually very difficult to match the modes of optical fibers to those of minute devices or to adjust their positions accurately. To solve such connection problems, the expanded core fibers are used, the aperture of the device is enlarged, and the optical path is shortened. In this paper, the concept of vertical photonics is discussed and the present status of the basic components (wavelength filters, polarizers, polarization splitters, etc.) and optical devices (isolators, optical switches, wavelength tunable filters, amplifiers, etc.) is reviewed.
Advanced optical packaging technology for practical integrated photonic modules
Authors: Nakajima Hirochika
Published: July 2007

For optical communication technology, which has been pushing for higher speed and larger capacity in the transmission trunk lines, the urgent tasks are not only improvements in performance but also the expansion of applicable areas by introducing new functions and moving into new phases.

For optical fibers to be applicable in access net, subscriber loop, intrastation transmission systems, and interprocessor connections, the realization of optical links that are easy to use, easy to fabricate; and inexpensive, is strongly demanded. Also, the appearance of optical nodes everywhere in the broad bandwidth network that will be the backbone of the multimedia society would not be too far off. Research on integrated optical devices and circuits that have new structures for waveguide‐type devices, array components, or two‐dimensional devices, is continuing to progress to meet these demands.

To mount these devices and circuits compactly and inexpensively into packages and modules, innovative packaging techniques have to be developed correspondingly. From this viewpoint, this paper reviews optical packaging technology, which holds the key to the realization of integrated photonics.
Iterative finite difference beam propagation method analysis of nonlinear optical waveguide excitation problem
Authors: Yokota Hirohisa , Hira Masafumi , Kurazono Sadao
Published: July 2007

The beam propagation method (BPM), used widely for analyzing optical waveguides and optical circuits, is also being applied to devices that include nonlinear materials. However, in the analysis of nonlinear optical devices using the conventional BPM, in many cases it is assumed that the field intensity distribution does not change within the step length in propagation direction. Therefore, for accurate calculation, the step size in the propagation direction must be extremely small, which results in long calculation times.

Therefore, this paper proposes and formulates a numerical method where the solution is forced to converge by the iterative calculation of a difference equation over each propagation step of the Crank‐Nicolson BPM method. Using this method, first, we analyzed the case where the fundamental TE mode propagates in the dielectric slab waveguide that has a Kerr‐like nonlinear cladding. By calculating the emission angle of the optical beam into the cladding, the present method is compared with the conventional method. After it is demonstrated that this present method is effective, the dependency of the optical beam emission angle for the incident power is shown. Furthermore, the effect of the beamwidth on the excitation is analyzed in the case where a nonlinear stationary wave is excited by a Gaussian beam and the interesting results are proved.
Analysis of piezoelectric transformer using a width‐shear mode
Authors: Wakatsuki Noboru , Ueda Masanori
Published: July 2007

An LiNbO3 single crystal has large electromechanical coupling efficiency, and its elastic loss is small. Using the elastic energy trapping phenomenon of an LiNbO3 single crystal, a piezoelectric transformer can be formed using a width‐shear mode. To reduce the internal loss, a high‐order mode of width vibration is used and multiple pairs of interdigital electrodes formed on the top and bottom surfaces of a piezoelectric substrate are used for both input and output.

To analyze the performance of a piezoelectric transformer with interdigital electrodes, Mason's equivalent circuit is used. Finally, the relationship between the designed parameter by the new equivalent circuit and the characteristic of a piezoelectric transformer is investigated to compare the theoretical and experimental results. In particular, it is proved that the ratio of input voltage to output voltage is determined by the load to the transformer and the number of interdigital electrode pairs for the input and output.
Millimeter‐wave active integrated antennas utilizing harmonics
Authors: Kawasaki Shigeo , Itoh Tatsuo
Published: July 2007

This paper reports an active integrated antenna which combines the antenna function with the millimeter‐wave MMIC technology. TJI addition to a high carrier frequency, the compactness of the circuit is extremely useful for applications to automobile radar and wireless LAN.

To realize low‐cost millimeter‐wave subsystems, this paper describes an active integrated antenna making use of the slot antenna and the second harmonic of the FET oscillator. The input impedance of the slot antenna is included in the design of a strongly coupled active integrated antenna array. The oscillation frequency of the array was evaluated by a large signal analysis.

In the case of a two‐element active integrated antenna using a harmonic, the second harmonic operating frequency of 39.3 GHz was obtained. The phase of the radiation of the fundamental mode was adjusted so that different radiation patterns for different modes were obtained. Also, in the uniplanar‐type four‐element array, a large signal analysis was carried out including the discontinuities in the coplanar waveguide. Through the present trial fabrication, the fundamental data for fabrication of millimeter‐wave monolithic active integrated antennas were obtained.
Design of super wideband electromagnetic wave absorber and its characteristics
Authors: Naito Yoshiyuki , Anzai Hiroki , Mizumoto Tetsuya
Published: July 2007

By combining a ferrite‐type electromagnetic wave absorber and a lossy dielectric layer, an electromagnetic wave absorber with a super wideband characteristic can be realized. In this paper, a grid‐type ferrite absorber and a rubber ferrite loaded ferrite multilayered absorber are treated as a ferrite‐type absorber. When a lossy dielectric material is mounted in front of these ferrite‐type wave absorbers, the thickness of a lossy dielectric layer necessary for realization of a return loss of more than 20 dB at any frequency above 30 MHz was computed. It was found that the thickness is much less than that for the lossy dielectric attached to a single layer ferrite. Further, by means of a model experiment in the coaxial tube, the thickness of the lossy dielectric layer was proven to be smaller if a lossy dielectric is combined with the grid‐type ferrite absorber loaded with rubber ferrite.
Electromagnetic power flow and its expression—poynting vector and Nukiyama vector
Authors: Hosono Toshio
Published: July 2007

Usually, the Poynting vector is considered to be a vector field expressing the power flow. However, in many textbooks on electromagnetics the following statements are given which cause confusion: (a) since an arbitrary vector field with zero divergence can be added without violating the energy conservation law, the Poynting vector is not a unique expression for the power flow; and (b) the Poynting vector has nonzero value near a charged magnet. Since it cannot be accepted that a power flow exists in such a space, the Poynting vector may not represent a power flow.

Such statements which cause confusion come from the education in which the relativistic aspects of electromagnetic theory have not been considered seriously. This paper is intended to contribute to the electromagnetic education and presents: (a) a clear explanation for the fact that the electromagnetic theory is essentially relativistic; (b) an explanation why the Nukiyama vector does not replace the Poynting vector; (c) general conditions to be satisfied by a vector which can be added to the Poynting vector; and (d) the basis on which we take the Poynting vector as the only expression for the power flow density.