bluuebunny/crossref_metadata_2025 huggingface dataset:
Network configurations for leased circuits in metropolitan areas
Authors: Hoshi Keiichi , Kawata Takao
Published: July 2007

With the rapidly increasing demand for leased service, an important issue in the future telecommunication network will be efficient utilization of leased circuits.

This paper considers the network configuration for leased circuits in the metropolitan area, where the demand for such circuits is increasing. This paper also discusses the allocation of cross‐connect (XC) nodes in the construction of the network for low‐speed leased circuits and the segregation/sharing of public and leased circuits from the viewpoint of economy.

First, the system configuration for the low‐speed leased circuits and the network topology for the efficient operation of the leased circuits are discussed. As a result, allocation schemes for XC nodes and schemes for fiber segregation and transmission capacity are proposed. Then the relation between the number of XC nodes and the network cost, as well as the relation between the transmission capacity and the network cost, are discussed from the viewpoints of the segregated and the shared configurations for the leased and public circuits. From this discussion, the optimal XC node allocation and the optimal transmission capacity are shown. Finally, a comprehensive assessment is described and the optimal area for each of the proposed network configurations is shown quantitatively for the case where the demand for the leased circuit or the equipment cost is varied.
Long‐span 2.5‐gbit/s cpfsk coherent optical transmission system employing high‐output power edfa boosters
Authors: Hayashi Yoshihiro , Ohkawa Norio , Yanai Daisuke , Ito Takeshi
Published: July 2007

This paper explains a system configuration for long‐span applications of repeaterless optical transmissions for their corresponding efficiency. From the results of a year‐long field test and in‐house experiments, the practicality of the CPFSK heterodyne delay demodulation method for 2.5 Gbit/s using a high‐output optical fiber amplifier has been evaluated.
A versatile two‐dimensional device simulation program and its application to NMOS
Authors: Ueda Jun , Namba Yoichi , Sakamoto Koichi , Miyoshi Tatsuro , Ushio Shintaro
Published: July 2007

The versatile algorithms of two‐dimensional device simulation programs are studied in detail. We have separated the device simulator which is independent of the device structure and the user's analysis purpose, and the preprocessor that specifically deals with user interface. Moreover, the algorithms of the device simulator become the discretization by information obtained at the nodes only, electrode current definition at the nodes of electrodes, initial guess using two‐dimensional numerical depletion approximation, and the iterative operation of the device simulation by step design. Using these algorithms we developed a two‐dimensional device simulator UNISAS, and confirmed the validity of the versatile algorithm using an example of NMOS. Step design is used for the analysis of the avalanche phenomenon of NMOS. Solving for the two carriers, we have explained easily the flow of electrons and holes in the avalanche breakdown phenomenon. Moreover, by changing only input data, we have easily analyzed the five‐gate NMOS.
LSI fabrication process evaluation system utilizing simulators
Authors: Tazawa Satoshi , Kubota Katsutoshi , Wada Kou
Published: July 2007

We propose a process evaluation method using channel‐doped MOS devices and process/device simulators for quantitative evaluation of contamination and surface condition. The amount of contamination is determined by comparison of the measured and simulated C‐V characteristics of an MOS capacitor. Then the MOS FET is evaluated by comparison with a theoretical ideal I‐V characteristic calculated from the MOS capacitor measurement data and the doping profile. The surface condition is evaluated by determining the carrier mobility from MOS FET characteristics. With these evaluation methods, we develop a new process evaluation algorithm to determine the cause of processing irregularities, whether due to contamination, damage, faulty pattern delineation, or other factors. By combining a process data base and process device simulator, we develop a process evaluation system to facilitate application of the new evaluation method. It is applied to the evaluation of MOS LSI processing.
Modeling of etching process via kalman filter and channel length control
Authors: Matsuba Ikuo , Matsumoto Kuniaki , Kobayashi Kazunari
Published: July 2007

In semiconductor fabrication it is difficult to form channels with precisely controlled lengths, even when using plasma etching which itself is highly precise. This is because of fluctuations in the processes preceding the etching, as, for example, in the developed resist dimensions. This paper proposes a method for controlling channel lengths which relies on an optimized over‐etching, the extra etching time after the normal etch completion depending on the variation in resist dimension, etc. In the method a phenomenological model is set up for the rate of change of channel length as a function of the resist dimension and etching cross section, and the polysilicon layer thickness and its phosphorus doping density as determined by sheet resistance. The model coefficients are estimated by a Kalman filter on wafer and lot measurement data. The results of production line experiments with the present method show a reduction in channel length variation by one‐half compared with the previous uncontrolled method.
Light polarization control due to electrooptic effect
Authors: Kido Yasuaki , Furuya Kazuhito , Suematsu Yasuharu
Published: July 2007

An analysis and experimental results are described for the automatic polarization control of the polarization plane of the output light from a single‐mode fiber with a standard axisymmetric core. This automatic polarization control device consists of two phase shifters made of z‐cut LiNbO3 exhibiting the electrooptic effect. The phase shifters are oriented with their transverse planes inclined to each other. The state of the polarization is detected by two Rochon prisms and is fed back to the phase shifters. The analysis has been done for the change of the polarization of the incident light in the polarization control device. The range of the voltage applied to the phase shifter for the control and the condition of the angle between the phase shifters are clarified. Next, experiments have been performed and the single polarization control in the desired direction has been attained. A proposal is made to simplify the control mechanism.
Computer simulation of bulk‐charge transport in small‐geometry depletion‐mes charge‐coupled device
Authors: Yonei Kenji , Omoto Osamu
Published: July 2007

This paper deals with a comparative investigation of small‐geometry Schottky‐barrier CCD with a depletion‐MES structure (depletion‐MESCCD). It also presents the performance evaluation of Si and GaAs D‐MESCCDs with three‐phase, low‐voltage clock pulse drive. Consequently, Poisson and continuity equations are put in difference form and a program for computer simulation of the behavior of electrons and holes in the device is developed. Simulation yields the relationship between the transfer electrode spacing and the potential and permits analysis of the carrier density, potential, leakage rate and transfer inefficiency during the charge transfer process. The results show that the potential profile of complete charge transfer with 1.2 Vp‐p of three‐phase clock pulse voltage, electrode length 0.5 μm and interelectrode distance 0.5 μm can be obtained. For CCD charge transfer with 0.6–2.0 Vp‐p three‐phase clock pulse, the leakage between bits is found to be the largest among the charge transfer leakages from all parts of the CCD. The simulation for a 1.5 Vp‐p three‐phase ramp waveform clock pulse shows that, if the charge transfer speed difference between Si‐and GaAs‐D‐MESCCD due to mobility difference is excluded, they give about the same performance.
Laser annealing of polysilicon films with an applied electric field
Authors: Okamoto Kotaro , Suzunaga Hiroshi , Kitagawa Yasuhiro
Published: July 2007

Polysilicon films deposited on an SiO2 substrate by pyrolysis of SiH4 were annealed with a Q‐switched ruby laser while an electric field was applied simultaneously. Investigating the effet of the laser‐excited photocurrents on the anneling showed that besides a general Joule heat promotion of the annealing, there was an elongation of the crystal grains in the direction of the electric field. The effect of the electric field in causing this improvement in crystallinity can be modelled by supposing that at above about 40 MW/cm2 where annealing starts to appear, the process is a solid‐phase coalescence caused by localized heating at the high resistance grain boundaries. Then at 70 MW/cm2, the process changes into a melt recrystallization process where random nucleation is suppressed by the Joule heating. Current‐assisted laser annealing of polysilicon deposited on a grating showed that the grating steps acted as nucleation sites and that there was crystal grain elongation perpendicular to the grating direction.
High‐speed photodetectors using GaAs MESFET
Authors: Umeda Tokuo , Cho Yoshio
Published: July 2007

This paper deals with experimental investigations of light response performance and operation mechanisms of the GaAs MESFET when used as a high‐speed photodetector. The GaAs MESFET under test is a device used for a microwave amplifier with 1‐μm gate length and 75 ˜ 300‐μm gate width. The illuminating light is either CW (He ‐ Ne) or pulsed (dye laser with 10‐psec pulse width and 7‐nsec pulse interval). The light is focused by the object lens and illuminates the area between the source and drain within 5 μm. When the FET is in the pinchoff state the pulse response is shown to be much improved. The output current depends on the input light power and tends to saturation. Light response speed of 100 psec can be obtained from a sample with 75‐μm gate width. Observation shows that the response speed is independent of gate width. From these experiments as well as the I‐V characteristics under illumination and the appearance of the gate voltage of the I‐V characteristic without illumination, it is shown that the depletion layer is changed. Based on these observations the operation model is proposed. Guidelines for optimizing the high‐speed FET photodetector (i.e., improvement of the surface configuration for illumination, selection of the active layer and carrier density and the requirements of the surface window layer) are presented.
Analysis of oscillation characteristics for the raman‐type free‐electron laser utilizing a two‐dimensional periodic magnetic field for the pumping source
Authors: Nakano Hayato , Shiozawa Toshiyuki
Published: July 2007

A two‐dimensional model of the Raman‐type free‐electron laser is considered. It is composed of a relativistic electron beam drifting in a parallel plate waveguide, immersed in a magnetostatic pump field with periodic variation in the direction of flow of the electron beam. For the model of the Raman‐type free‐electron laser specified here, a theoretical study on the oscillation characteristics is presented and the following results are obtained. First, the spatial growth rate of the scattered wave can be maximized by properly adjusting the ratio of the beamwidth to the separation between conducting plates of the waveguide. The magnetostatic pump field affects the growth rate through its magnitude on the beam surface and its wave number. Second, the growth rate of the scattered wave is enhanced and its frequency is lowered as the wave number of the periodic magnetic field decreases, while the former is reduced and the latter becomes higher as it increases. Third, the generation of higher‐order modes can be suppressed by reducing the wave number of the periodic magnetic field.
M2O‐Al2O3‐SiO2 glass gate PNA and pK ISFETs
Authors: Shoji Shunichi , Esashi Masayoshi , Matsuo Tadayuki
Published: July 2007

To improve the capability of the ISFETs for measuring pNa and pK in living bodies, the ion selectivity of its sensor M2O‐Al2O3‐SiO2 (MAS, where M is an alkali metal) glass membrane was studied. The MAS membrane has been used as an ion‐sensitive membrane of pNa and pK glass electrode and it has been known that its selectivity depends on the composition of the MAS membrane. To obtain the maximum ion selectivity of the pNa and pK ISFET, the relationship between the ion selectivity and the composition of the MAS membrane was investigated by measuring the ion selectivity over various compositions. It was confirmed that the selectivity of the MAS gate ISFET between Na+ ions and K+ ions depends on both the kind of alkaline cation and the ratio of the alkali metal to aluminum in the MAS membrane. As a result, the best composition of ion‐sensitive membranes for pNa and pK ISFET was determined. A pNa ISFET was obtained which uses the LAS membrane containing Li as the alkali metal and has a selectivity of about 200 times for Na+ ions against K+ ions with a low output‐voltage drift and a long life. A pK ISFET also was obtained which uses a KAS membrane containing K and has a selectivity of about 40 times for K+ ions against Na+ ions.
Self‐aligned bipolar transistors fabricated by selective etching of polysilicon technology
Authors: Uehara Keijiro , Higuchi Hisayuki , Iijima Shinpei
Published: July 2007

To fabricate submicrometer transistors practical for LSI by conventional photolithography with a minimum pattern width of 1.5 μm, a self‐aligned process using a selective etching of polysilicon technology (SEPT) has been developed. Compared with the formation of fine patterns by side etches of overhangs, this process, using an oxide thickness and a diffusion distance as a pattern width, has a high accuracy and reduces the variation of the base voltage (VBE) which becomes an important characteristic when the emitter size is reduced by a self‐alignment technique. In this method of self‐aligning the base contact and the emitter, a submicron transistor with emitter width of 0.8 μm, base‐emitter spacing of 0.4 μm, and the base contact width of 0.3 μm can be fabricated with a mask pattern of 1.5 μm width. By the reduction of the active region, the junction capacitance and the base resistance which affect the high‐speed performance have been reduced drastically. A 25‐stage, 3‐input ECL ring oscillator designed with practical rules of 1.5 μm minimum pattern width and 4.5 μm interconnection pitch has shown a delay of 95 ps (ICS = 0.78 mA). Since this method has a high‐dimensional accuracy and reduces the VBE variation which becomes an important characteristic for LSI, it can be used in further scaling.
A switched‐capacitor digital capacitance meter
Authors: Kondo Kazuyuki , Watanabe Kenzo
Published: July 2007

A capacitance meter using switched‐capacitor circuits is developed. The capacitance under measurement is first sampled in its proportional voltage, which is then converted into the binary number by means of the cyclic analog‐to‐digital conversion. A prototype meter built using discrete components has achieved the resolution of 9 bits, measurement time of about 0.4 ms, and error less than 0.7 percent. The effect of the capacitance mismatch and clock feedthrough upon the measurement accuracy is analyzed for both the discrete and MOS IC realization. The analysis shows that 10‐bit accuracy is obtainable if the capacitance mismatch less than 0.06 percent is achieved by MOS IC realization.
Generation of electron beams by low–temperature field emission
Authors: Matsuda Jin‐Ichi , Kubo Mitsunori , Iriguchi Chiharu , Kato Kazuo , Yamashita Tsutimu , Masuda Takao
Published: July 2007

A method is proposed of generating a fine electron beam which has an excellent monochromaticity and high brightness by using an extremely low temperature and high electric field. This paper describes the actual apparatus based on the proposal. If the cathode of the apparatus is kept at an extremely low temperature (about 4K), theoretically, the possibility exists of making the energy spread as small as of the order of 0.01 eV, while the energy spread of a conventional electron beam at room temperature with a high electric field is of the order of 0.1 eV. The prototype apparatus assembled consists of a 3‐electrode type electron emission system, the main part containing a retarding potential energy analyzer and a vacuum chamber (about 10−9 Torr) made of stainless steel. Polycrystal tungsten wire is used for the cathode. The reduction of the energy spread was not achieved for the theoretical value, because of the deposits on the tip surface due to the residual gas (notably oxygen) at the extremely low temperature (cooled by liquid helium). At a low temperature (cooled by liquid nitrogen), however, the energy spread was improved by 25% compared with that at room temperature. This shows a possible improvement of the energy spread by cooling the cathod as expected.
Reproducing process of perpendicular magnetic recording
Authors: Tanabe Shinji , Iwasaki Shun‐Ichi
Published: July 2007

The reproducing process of perpendicular magnetic recording is here analyzed by a finite element numerical simulation. A mechanism is found for significant improvement of reproduction sensitivity by means of a soft magnetic layer backing a CoCr medium. The analysis is conducted for a vertical head consisting of main and auxiliary magnetic poles. The magnetic field saturation and reduction are taken into account in iterative calculation based on the Newton‐Raphson method. In calculation of the magnetic field reduction a measured M‐H loop for CoCr including the minor loop is used. It is found that the soft magnetic backing layer increases by an order of magnitude the amount of magnetic flux flowing deep into the main pole. This finding confirms experimental observation that the reproduction output increases by an order of magnitude with the backing layer. The paper also describes the spacing loss in reproduction of perpendicular recording. A more useful definition of reproduction efficiency of the head is found from the above results. The computation procedure is useful in analysis of a nonlinear reproduction process.
Analysis of a ringing choke converter
Authors: Ninomiya Tamotsu , Higashi Tooru , Harada Koosuke
Published: July 2007

The ringing choke converter is widely used as an electronic power supply with a small capacity. A number of works have been published on the feedback systems for adjustment of output voltage. No sufficient analysis, however, has been undertaken on the static and dynamic characteristics. In this paper, a nonlinear differential equation describing the basic operation is first derived. Next, from a small signal model obtained from this differential equation, a loop transfer function of the converter is derived. Further, the transfer function for an input variation and a load variation under regulation have been derived. As a result, the characteristic equation becomes linear and it is shown that the converter is extremely stable. The dynamic characteristic parameters of the ringing choke converter are found different from those of the conventional reactor current discontinuity mode converter. Both the gain bandwidth product of the loop transfer function and that of the transfer function of the output voltage fluctuations for the input voltage fluctuations under regulation are smaller in the ringing choke converter than in the reactor current discontinuous mode converter. It is found that the ringing choke converter is less susceptible to the input voltage fluctuations and operates with a greater stability than the reactor current discontinuous mode converter.
Evaluation of contact resistance characteristics for tin plated connector contacts in accelerated degradation test
Authors: Yasuda Kei‐Ichi , Aoki Takeshi , Imori Yasutaka
Published: July 2007

To find applicability of tin/tin contacts to connectors used in communication systems requiring high reliability electrical connection, damp heat cycle tests have been carried out and the accelerated degradation characteristics of the tin/tin contact have been compared with those of the gold/gold and gold/tin contacts. The results are as follows. (1) The contact resistance of the tin/tin contact is close to that of the gold/gold contact and it was found to be a reliable contact in high reliability connectors for the first 20 insertions. (2) In the tin/tin contact, the worn‐off area is smaller and the apparent contact area is larger than in the gold/tin contact. These factors contribute to the stability of the contact resistance and are basis for contact resistance in the tin/tin contact is more stable than in the gold/tin contact. From these results it is found that the tin/tin contact can be used in high reliability connectors within the range of a few insertions.
Photoconductive characteristics and stabilization of hydrogenated amorphous silicon films
Authors: Takahashi Minoru , Nozawa Toshinori
Published: July 2007

This paper describes the changes in the photoconductive characteristics under elevated environmental conditions and presents a stabilizing method of hydrogenated amorphous silicon (a‐Si:H) thin films. a‐Si:H is decomposed from silane in a PCVD (Plasma Chemical Vapor Deposition) apparatus. The results of high‐temperature and high‐humidity storage tests reveal that the photocurrent increased by about two orders of magnitude over the initial value, followed subsequently by a gradual decrease. The data analyzed through ESR, SIMS and IR absorption spectroscopy confirmed that these photocurrent changes are closely related to the reduction of dangling bonds, exodiffusion of hydrogen and gas adsorption, such as H2O molecules, onto the film surface. The characteristics were stabilized through coating the film surface with a silicon nitride film deposited at room temperature by ECR (Electron Cyclotron Resonance) plasma CVD.
Effective cutoff frequency of LP11 mode in uniformly curved step–index optical fibers
Authors: Tanaka Toshiaki , Morita Nagayoshi , Kumagai Nobuaki
Published: July 2007

This paper evaluates the field distribution and the propagation constant of the LP11 mode propagated in circularly bent step‐index optical fibers by considering these quantities as perturbations from those in the straight fiber. By using these results, the field distributions and the curves of solutions of the eigenvalue equations for the bent fiber are studied in detail based on numerical and physical considerations. On the basis of this study, a reasonable method is proposed for defining the effective cutoff frequency of the LP11 mode in a circularly bent section of a step‐index fiber. Also, an easier method of obtaining the approximate value of this effective cutoff frequency is presented. It is confirmed that the effective cutoff frequencies calculated according to the definition proposed herein become very close to those effective cutoff frequencies used until now, i.e., those values based on the difference between the measured losses of the LP11 mode and the LP01 mode.
Characteristics of pattern peak–shift in digital magnetic recording
Authors: Nishikawa Masaaki , Kirihara Akio , Doi Yukihiro
Published: July 2007

Pattern peak‐shifts due to the interference of adjacent magnetization transitions in digital recording are one of the main causes of limiting its recording density. This paper aims to supply design data on pattern peak‐shifts, giving experimental data of peak‐shift in various transition patterns, and comparing them with the calculated results obtained from the superposition of isolated read signals. A magnetic tape system was used in which a nonlinear interference effect occurs easily during the write process.

The relationship between the peak‐shift in a magnetic transition pattern Δx and the minimum magnetic transition interval b is given in a normalized graph coordinated by Δx/b and b/(W50/2), where W50 is the half‐width of an isolated read signal. For example, the design value of b/(W50/2) for required value of Δx/b ≤ 25% is about 1.3, 1.0 and 1.2 or greater for the NRZ‐I, FM and MFM code systems, respectively. The nonlinear interference in a recording process occurs so that each magnetization transition is pushed toward the direction of medium motion. In a region where this effect occurs strongly, the calculated results do not agree with the actual ones.
Elimination of spurious solutions in vectorial finite–element analysis of dielectric waveguides–A method using transverse magnetic–field component
Authors: Hayata Kazuya , Koshiba Masanori , Eguchi Masashi , Suzuki Michio
Published: July 2007

This paper formulates a new finite‐element representation for the vector analysis of dielectric waveguides, using the transverse magnetic‐field component. This approach starts from the earlier finite‐element formalism using all magnetic‐field components. Considering the condition V Δ H × 0 by the same technique as in the master‐slave method, and eliminating the longitudinal magnetic‐field component, the equation only for the transverse magnetic‐field component is derived and solved. By this scheme, the spurious solutions (nonphysical solutions), which have been produced inevitably in the earlier vector finite‐element analysis, is now eliminated completely from both fast‐ and slow‐wave regions. To verify the validity and the effectiveness of the present scheme, the analysis is made for a dielectric‐loaded rectangular waveguide. The results of analysis are compared with those of exact analysis and by other methods, indicating the effectiveness of the present finite‐element formulation. The present method does not involve any arbitrary constant, such as the penalty coefficient in the penalty method. The size of the matrix equation to be solved is two‐thirds that of the penalty method, which improves the efficiency of numerical computation considerably.
SH wave device for HF–band frequency modulator and demodulator
Authors: Toda Kohji , Mizutani Koichi
Published: July 2007

This paper describes the shear horizontal (SH) wave devices for frequency modulation and demodulation in the HF band. By means of a numerical analysis, it is found that the zeroth‐order symmetric SH mode in a horizontally poled piezoelectric ceramic plate is useful for this purpose. It has a low dispersion, low velocity and high coupling coefficient. SH wave devices as small as IC chips are useful in the HF band. The frequency characteristics of the frequency modulator and demodulator are from dc to 200 kHz and their linear conversion bandwidth is 60 kHz. These devices are useful for signal processing devices and sensors in the HF band.
Structural and electrical properties of V3Si films formed by solid–phase–reaction
Authors: Sorimachi Yoshio , Matsumura Tamio , Yamashita Tsutomu , Tsubata Ichiro , Miyauchi Shinnosuke
Published: July 2007

This paper describes the structural and electrical properties of V3Si films formed by solid‐phase‐reaction for Josephson superconductive thin‐film devices. To evaluate the film structure, the high‐speed ion backscattering technique, X‐ray diffraction technique, and SEM technique were employed. The resistivity of the film was measured by the four‐terminal method at temperatures between 4.2 and 300°K. In addition, the sueprconductive transition temperature was obtained. From these results, the following observations were made: (1) the V3Si phase is formed by using a V film on a thermally oxidized Si substrate, but there is a minimum SiO2 thickness depending on the temperature for the thermal treatment; (2) a V3Si film can be formed on either amorphous silica glass or single‐crystalline quartz. However, when the V3Si film forms on the silica glass, it tends to crack and has a large ΔTc. When the film is formed on a single‐crystalline quartz, there is a strong growth preferentially, and ΔTc is smaller; (3) Tc is dependent on the thickness of the V film and the thickness of the V film should be more than 1500 Å to obtain Tc higher than 10 K.
Laser damage threshold of KDP single crystal at 1.053 μm
Authors: Shimomura Osamu , Yokotani Atsushi , Sasaki Takatomo , Yoshidas Kunio , Yamanaka Chiyoe
Published: July 2007

Large KDP crystals having a high damage threshold against laser light are required for harmonic generation of a 1.053 μm high‐power glass laser system for nuclear fusion experiment. We studied the internal damage threshold of KDP crystals at 1.053 μm, 1‐ns pulsewidth.

For the crystals grown by the temperature falling method, the damage thresholds of 8.3, 7.3, 6.1, and 11.2 J/cm2 were obtained for the KDP samples having a laser irradiated surface cut perpedicular to the (010) direction ([010] sample), parallel to the (101) surface ((101) sample), type I cut (type I sample), and type II cut (type II sample) of phase matching angle. The sample cut from the prismatic sector showed an anomalously large value of threshold 34 J/cm2.

For the crystals grown by the electro‐dialysis method, 3.3, 5.0, 5.9, and 6.9 J/cm2 were obtained for “[010],” “(101),” “type 1,” and “type II” samples, respectively.
Ar pressure dependence of saturation magnetization and film composition in TbCo and tbfe sputtered films
Authors: Ohbayashi Shigeki , Nawate Masahiko , Honda Shigeo , Kusuda Tetsuzo
Published: July 2007

The argon pressure dependence of saturation magnetization MS and film composition in TbCo and TbFe sputtered films under the substrate bias VB × 0 was investigated. It was found that the change in the shape of multitarget surfaces influences MS strongly. When the sputtering period was 60 min, the Ar pressure dependence of MS and the film composition were different in TbCo and TbFe films. This was found to be due to the existence of the composition gradient in the direction of the film thickness in the TbFe film deposited under high Ar pressure. As a result of investigating the multitarget surfaces, the Tb chip surface was found to be contaminated by TM atoms (Co, Fe) and the intermetallic compound was formed. On the other hand, the TM target surface was clean. The surface condition of the Tb chip was different in the Tb ‐ Co and Tb ‐ Fe multitargets. The Tb surface of the Tb ‐ Fe target was covered with cone‐shaped projections, causing the composition gradient in the film thickness direction when the Ar pressure was high. When the sputtering period was short (shorter than 12 min), the composition ratio against NTM/NTb) against MS and Tb decreases with the increase of Ar pressure in both depositions of TbCo and TbFe films.
Wide Frequency‐Modulation Operation of Semiconductor Lasers Using a Composite‐Optical Cavity
Authors: Nagata Masaya , Ohtaka Masato , Kobayashi Takao
Published: July 2007

In the optical heterodyne communication and measurement based on semiconductor lasers, selection of an arbitrary frequency within a broad gain spectral width and continuous and broadband FM operation are needed. This paper reports a theoretical study on a laser diode (LD) with a composite optical cavity using an external reflector. Using a GaAlAs LD with an adjacent plane or spherical mirror, a broadband tuning of oscillation frequency of about 8 THz (18 nm) becomes possible by variation of the external cavity length. Further, by modulation of the injection current, a continuous FM shift as large as 150 to 290 GHz is realizable which is three to five times the conventional value.
Study of GaAs FET process using focused ion beam lithography
Authors: Sasak Yoshinobu , Morimoto Hiroaki , Komaru Makio
Published: July 2007

To construct a highly efficient GaAs FET, it is effective to shorten the gate length. Focused ion beam lithography was utilized to form fine gates. For application of this technique to practical device fabrication, the exposure characteristics of PMMA and the damage to the substrate by the Si‐and Be‐focused ion beams have been investigated. A stable resist profile was obtained with a dose of 2 × 1013 ions/cm2. However, the exposure to the ion beams damaged the substrate. To eliminate this damage, a deep recessed structure was adopted and focused ion lithography was used for fabrication of an FET with low noise and medium output power. A gate length of 0.2 to 0.3 μm was realized and an improvement of the device characteristics was demonstrated. As the device structure becomes finer, the gate resistance increases. Therefore, a mushroom gate was formed to decrease the gate resistance. It was shown that focused ion beam lithography is an effective way to form an efficient GaAs FET.
Proposal of high speed bipolar‐CMOS merged VLSI technology and its future prospect
Authors: Watanabe Atsuo , Hiraisi Atsusi , Nagano Takahiro , Masuda Ikuro , Ikeda Takahide
Published: July 2007

BiCMOS technologies are one of the promising candidates for the third generation LSI technology because it realizes high‐speed, high‐integration VLSIs utilizing the features of both the CMOS and bipolar devices. This paper discusses the device structure with respect to the speed‐up of BiCMOS basic circuits. First, the modeling of basic circuits and the numerical analysis of the bipolar operation indicate the importance of the vertical dimension of bipolar devices. Next, we have discussed a vertically miniaturized well structure without the degradation of the CMOS characteristics. A theoretical analysis clarified that the buried well structure with the combination of the shallow diffusion layer and the buried layer produces the minimum point of the impurity density and realizes both high‐speed bipolar device and fine‐pattern CMOS devices. On the basis of this, we have fabricated 1.2 μm gate CMOS devices and high‐speed bipolar devices with the break‐down voltage of 8 V and the maximum cut‐off frequency of 9 GHz on the same substrate and confirmed that the basic circuit constructed with these devices exhibits the delay time of 0.4 ns with the typical load capacitance and operating frequency. Furthermore, it is indicated that the performance of this basic circuit proceeds with the same ratio as that of CMOS circuits' devices based on the scaling law.
A 1‐GHz band low‐power dissipation GaAs prescaler IC
Authors: Maemura Kosei , Shimura Teruyuki
Published: July 2007

It is important that the power consumption by mobile communication equipment be reduced as much as possible from the viewpoint of miniaturization, weight reduction and battery operation. One approach to this problem has been the development of a dual modulus prescaler IC for 1/128 and 1/129 division in the 1‐GHz band with GaAs FET's capable of high‐speed operation and low power consumption. Since nonuniformity of device characteristics is still substantial in GaAs FET's, an optimization in the circuit design is needed whereby the characteristics of the FET are given sufficient consideration. In the design of the prescaler, the SCFL is used as a logic gate which has a broad tolerance in characteristic fluctuations of the FET. In addition to consideration of the operating margin and fan‐out characteristics, such design optimizations as the pattern orientation of the IC and the current distribution to each part have been carried out. With only one 5‐V power supply, the power supply current required has been less than 5 mA in the 1‐GHz band. This power consumption is less than half that used by the conventional SiECL IC. The design procedure and the results of the test fabrication are reported.
High–power HeCd+ white light laser
Authors: Fuke Akira , Masuda Katsuhiko , Tokita Yasuhiro
Published: July 2007

The hollow cathode HeCd+ laser includes twelve oscillation lines. The oscillation line of 441.6 nm (blue), 533.7 nm and 537.8 nm (green), and 635.5 nm and 636 nm (red) in the visible area can be oscillated concurrently by using wide‐band mirrors for a resonator to produce a white light laser. This laser is expected particularly in the image production industry because a single laser tube allows the three primary colors of light to be produced and the green wavelengths are optimum for green emulsion of photographic films. However, it has been difficult to produce the hollow cathode HeCd+ laser of continuous oscillation and high power. We have investigated the high power and output stability of the white light laser for practical purposes. As a result of examining the structure of the hollow cathode as a means for high‐power laser, we could realize a high‐power HeCd+ white light laser by using a new structure which was an improvement over the conventional flute type. This paper explains the structure of the hollow cathode and shows the dependencies of the output on the Cd vapor pressure, He pressure, input power for the cathode length of 61 or 43 cm, and the noise characteristics for the cathode length of 61 cm.
Single‐mode optical fibers with zero total dispersion at wavelength 1.3 and 1.55 μm. fiber with α‐power index core and triple clad
Authors: Nakazawa Kazushige , Hinata Takashi , Hosono Toshio , Furukawa Shinichi
Published: July 2007

Single‐mode optical fibers with an α‐power index core (α = 1, 2, 6, ∞) and a triple clad have been designed under the following two conditions: (I) the total dispersion at wavelengths of 1.3 and 1.55 μm is zero; and (II) the cut‐off wavelength λc for the second mode is less than 1.15 μm. In this paper, the sensitivity of the total dispersion, the equivalent bending radius (the radius at which the bending loss is 0.01 dB/km), and the splice loss of those fibers are discussed. The clad has an ideal triple layer structure (the relative index difference between the first and outer cladding is Δ2 and that between the second and outer cladding is Δ3). For a given value of α which determines the core refractive index profile, Δ1. (the relative index difference between the core and outer cladding), and a (core radius) can be chosen freely. In this paper, for a given α the fiber, satisfying conditions (I) and (II), was designed under the conditions that (1) Δ1 = const, and (2) \documentclass{article}\pagestyle{empty}\begin{document}$ A\mathop \Delta \limits_ = \int\limits_0^{a/w} {n(r/w,\;\lambda)dr\; = - const(w\mathop \Delta \limits_ = a + t_1 + t_2, t_m;} $\end{document} m‐th cladding layer width, m = 1, 2). Comparing the fiber with a core of α = 1, 2 and 6 (t2/t1 = 1.0, Δ2 < 0, Δ3 < 0), the step index core fiber (α = ∞). has the following characteristics whether the fiber is designed under condition (1) or (2): 1) a lower sensitivity for the core radius and wavelength; 2) a smaller equivalent bending radius; 3) a smaller splice loss in the case where d/a = const (d: axial displacement). For the case where α = ∞, the structure with Δ2 > 0 and Δ3 < 0 was investigated and compared with the structure with Δ2 < 0 and Δ3 > 0.
Millimeter wave dielectric waveguide isolator
Authors: Tanaka Katsuyuki , Tsutsumi Makoto , Kumagai Nobuaki
Published: July 2007

A dielectric waveguide isolator with a new open structure is proposed which makes use of the magnetic loss of the ferrite. The analysis is not based on the conventional two‐dimensional approximation but is a rigorous three‐dimensional approach taking into account the waveguide width and is based on the mode matching method. From the numerical results, it is demonstrated that an isolator based on the TM excitation is possible which cannot be found by the two‐dimensional approach. Subsequently, the isolator is operated experimentally and the results are shown to agree well with the theoretical prediction. Further, as a method for development of the characteristics, the experimental results for the structure loaded with a lossy material are presented.
Guided modes of diffused slab waveguides
Authors: Yata Akira , Ikuno Hiroyoshi
Published: July 2007

The propagation constants and field distributions for the guided modes for diffused slab waveguides are evaluated by uniform asymptotic solutions. The effect of the upper layer of the substrate on the guided modes are obtained automatically by the use of parabolic cylinder functions of noninteger orders. Diffused waveguides which have complicated profiles of refractive index such as squared hyperbolic tangent and Gaussian profiles are considered. The accuracy of uniform asymptotic solutions is examined numerically. As a result, it was found that their solutions had a high accuracy and they clarified the behaviors of the fundamental mode in the frequency range for the single‐mode propagation. As analyses and design examples for a variety of waveguides, the relationship between the refractive index profile and the domain of the single mode propagation was examined. It was shown that the waveguides with Gaussian profile are superior to those with other types of profiles.
Fundamental study on a short distance measurement method by using a sinusoidal wave oscillator with light path as delay line
Authors: Sato Katsunori , Echigo Hiroshi , Takagi Tasuku
Published: July 2007

Conventional optical distance measurement systems are not convenient for short‐distance measurements. This paper proposes a system which can measure a short distance accurately and simply. This system is tested and investigated, and in this system, the optical path is contained in an oscillator. By changing the oscillation frequency by the optical path length, the distance is obtained from the frequency. From a portion of the experiment and a theoretical study, the possibility of a distance measurement system is investigated. The accuracy of the present system can be improved by raising the oscillation frequency. In the experiment, a 300‐m long optical fiber was measured within an error of 5.5 cm at the oscillation frequency of 1 MHz.
Analysis of groove guide for short‐millimeter waves
Authors: Tamura Hitoshi , Kurazono Sadao
Published: July 2007

Requirements for waveguides of millimeter waves are demanding. Ongoing works have been conducted seeking waveguides with better characteristics. Many consider groove guides to be promising waveguides for short millimeter waves based on their easy manufacture and small influences due to bendings. However, earlier works on groove guides have focused on rectangular grooves. Their analyses were approximate and there were no rigorous analyses. This paper rigorously analyzed three types of groove guides via the method of boundary elements. We obtained the electromagnetic fields of the transmitted modes and various transmission properties such as cutoff frequencies, dispersion characteristics and attenuation characteristics. As a result, we clarified that groove waveguides had low losses and low dispersion. In practice, it may be possible to realize their uses for short millimeter waves.
A multiple‐ISFET integrated with CMOS interface circuits
Authors: Tsukada Keiji , Maruizumi Takuya , Miyagi Hiroyuki
Published: July 2007

To achieve the simultaneous measurements of ion concentrations with high accuracy using multiple ISFETs, the integration of multiple ISFETs with signal processing circuits has been attempted. To achieve process matching in the fabrication of the ISFETs and additional circuits, and to lower the power consumption, CMOS devices have been used for the signal circuits. The integrated circuits were composed of four ISFETs, a constant current source, a buffer amplifier, and a multiplexer. To measure ion concentration at high speed with a high degree of accuracy, each ISFET contained a source follower and a buffer amplifier to achieve an independent operation. Only the output signal was switched by a multiplexer. The average sensitivity of each ISFET was 54.4 mV/pH for the range of pH 1 to 10. The response time for an increase of the pH by 1 was about 1 s. The time needed to switch the output signal was 200 μs, which is three orders of magnitude faster than ion response speed. As a result, it was found that this integrated sensor structure was suitable for measuring the response of multiple ISFETs at high speed. This paper describes the sensor structure, the circuit design and its response characteristics.
Aberration of GRIN—rod lenses in single—mode optical fiber devices
Authors: Sumida Masatoyo , Takemoto Kenji
Published: July 2007

Graded refractive index rod (GRIN‐rod) lenses are used widely in optical devices for optical fiber communication systems. Insertion loss is a major criterion for evaluating optical devices, especially those used in single‐mode fiber systems, and aberration is a dominant factor in insertion loss. Thus, aberration analysis is essential in designing high‐perfomance optical devices. This paper presents ray traces within the third‐order aberration when light propagates through GRIN‐rod lenses. Using the fact that the ray is the orthogonal trajectory of the wavefront, we derive a novel wave optical description of GRIN‐rod lenses to the degree of third‐order aberration. This paper shows the relatinship between coupling efficiency and lens parameters. The necessity of considering aberration effects in designing low insertion loss optical devices is shown. The experimental results are in very good agreement with the calculated values, and the validity of the present analysis is confirmed. This paper proves that GRIN‐rod lenses are superior to ball lenses in terms of aberration, and provide higher coupling efficiency.
Asymptotic approximation and experimental study of electromagnetic fields excited by an electric dipole located over a conducting concave spherical surface
Authors: Maeda Tadahiko , Sawaya Kunio , Adachi Saburo , Mushiake Yasuto
Published: July 2007

The dome antenna has been proposed for scanning an antenna beam at a high speed in a wide angular range. For the design of a dome antenna, an electromagnetic analysis in the concave side of the conducting sphere is required. In connection with this problem, the electromagnetic field by an electric dipole placed on the concave surface of an open conducting sphere has been reported and analyzed in terms of the sum of the whispering gallery (WG) modes, continuous spectrum and ν = 0 (ν: wavenumber in the θ direction) by the authors. However, it has been pointed out that this expression has a problem for an arbitrary ka, although it provides a valid result for ka = nπ/2 (k: wavenumber, a: sphere radius, n: integer). It is also unattractive numerically since Legendre functions must be calculated by numerical integration. In this paper, an engineering application is attempted by using a high‐frequency approximation. By means of the approximate asymptotic solution and the previous expression, actual numerical calculations have been carried out. By way of comparison with experimental results, the validity of each expression is confirmed and its range of applicability is studied.
Characteristics of MOS—FET PWM inverter with high carrier frequency
Authors: Nagao Michihiko , MacHitani Yooichi , Nakano Tadao
Published: July 2007

Since a power MOS‐FET has a reverse diode located internally between the drain and source, when a PWM inverter is constructed with MOS‐FETs, a shunt phenomenon occurs between the upper and lower arms due to the recovery current of this internal diode. This phenomenon can effectively be prevented by limiting the current rise by an inductance. In this work, a PWM inverter with around 1 kW has been realized which operates with a high carrier frequency of about 100 kHz by using a close‐coupled inductor. Furthermore, as a design guideline for a PWM inverter, an analysis is made of the loss of each device and inverter efficiency and the experimental results are compared.
Miniaturized directional coupler—type optical switches
Authors: Minakata Makoto , Sakano Toshikazu , Kawakami Shojiro
Published: July 2007

Optical switches not only find wide applications, but also are used in a matrix form. Hence, reduction of the single elements is important for improving the integration density and improving the characteristics of the bandwidth and insertion loss. In this paper, a fabrication guideline has been obtained for a miniaturized LiNbO3 directional coupler‐type optical switch. Next, based on the guideline, a device was fabricated, and the relationship of the waveguide spacing S to the coupling length L0 and the phase constant difference Δβ/C was measured by the monitor method using a metal loading. At the wavelength of λ = 1.15 μm, we obtained S = 1.7 μm, L0 = 1.6 mm (previously several millimeters) and Δβ/C = 0 as the minimum. Further, an optical switch with two divided electrodes was fabricated and the switch voltage of V0 = 12 V, extinction ratio of 9.8 dB, and optical insertion loss of 3.6 dB were obtained. Items to be investigated for further improvement are included.