bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of space charge and multiple scattering on the gain of an X‐ray free electron laser using stimulated transition radiation
Authors: Yoshimori Shigeru , Kawamura Mitsuo 
Published: July 2007

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

AbstractA multilayer monolithic microwave integrated circuit (MMIC) directional coupler is proposed in which the characteristics of the multilayer MMIC structure constructed with conductors and dielectric films on a GaAs wafer surface are used effectively. In the proposed directional coupler, a tight coupling of 3 dB can be realized with low loss and in a small area. It is highly flexible in design. Also, it is shown in this paper that by means of the proposed multilayer directional coupler, a millimeter‐wave variable attenuator, a balanced modulator, and an endless phase shifter can be realized. These structures play important roles as millimeter‐wave amplitude/phase control circuits. Hence, it is significant to accomplish miniaturization and MMIC realization.The multilayer directional coupler designed and fabricated in the 40‐GHz band exhibited a circuit area of 0.45 mm2and coupling losses of 4.0 ± 0.2 dB. The designed and measured values agree well. Further, the amplitude/phase control circuits were designed and also exhibited a good performance.
Fiber‐optic millimeter‐wave subcarrier transmission links using HBTs as photodetectors
Authors: Suematsu Eiji , Imai Nobuaki 
Published: July 2007

AbstractThe authors utilized monolithic microwave integrated circuits (MMIC) compatible devices, GaAs HBT and InP/InGaAs HBT, as photodetectors for a fiber‐optic/millimeter‐wave subcarrier link, and investigated the link loss characteristics, subcarrier‐to‐noise ratio (SNR) characteristics, and IM3 characteristics of the fiber‐optic millimeter‐wave subcarrier link, comparing them with those of the link using a pin photodiode. The link gain characteristics are compared with those of the links which use other MMIC compatible photodetectors (MSM and HEMT) and pin photodetectors (pin‐PD). It is found that for both the common emitter HBT link and the common‐base HBT link, good response and flat frequency characteristics can be seen over several gigahertz in the millimeter‐wave band.The SNR characteristics of the common emitter HBT link governs the noise characteristics of the optical/RF transducer in the low‐frequency region where there is internal gain. However, in the millimeter‐wave region (where there is no gain), it is dependent on the noise characteristics of the LNA connected after the HBT or in the common base HBT link. The input/output characteristics and IM3 characteristics of the HBT link are dependent on the power characteristics of the external optical modulator (EOM) when the optical power is less than ‐ 3 dBm.An optical/RF transducer combining an HBT photodetector, LNA, and horn antenna is designed. Using this optical/RF transducer, an optical fiber/millimeter‐wave radio link is designed and the FM video transmission characteristics are investigated experimentally. It is shown that this link was effective at wavelengths of 0.83 μm and 1.3 μm.
Finite‐element analysis of electron waveguide discontinuities with arbitrary potential and effective mass distributions
Authors: Gotoh Hitoshi , Koshiba Masanori 
Published: July 2007

AbstractFor the two‐dimensional discontinuity problems in an electron waveguide with arbitrary potential distributions and arbitrary effective mass distributions, an analysis method based on the finite‐element method is proposed and formulated. Specifically, the method is applied to a rectangular bend in an electron waveguide so that its validity and effectiveness are presented. Also, a formulation is carried out for a more practical electron wave circuit in which the potential outside the waveguide is finite. The formulation is applied to a rib‐type discontinuity in an electron waveguide and the transmission characteristics are analyzed. The results are compared with those for the case in which the potential outside the waveguide is infinite.
Method of evaluating facet and bulk degradation in semiconductor lasers
Authors: Fukushima Takehiro , Furuya Akira , Kito Yasuhiro , Sudo Hisao , Sugano Mami , Tanahashi Toshiyuki 
Published: July 2007

AbstractA new method has been proposed to evaluate bulk (crystal) and facet degradation in semiconductor lasers separately by cleaving the degraded laser diodes into three regions along a resonator direction. By applying the method to AlGalnP visible light laser diodes, it has been demonstrated that it is possible to evaluate the changes in facet reflectivity and the effects of bulk and facet degradation on performance characteristics of as‐cleaved laser diodes as well as laser diodes with antirefiection and high‐reflection (AR‐HR) facet coating.
A scalar finite element analysis of nonlinear optical channel waveguides using isoparametric elements
Authors: Niiyama Akira , Koshiba Masanori , Tsuji Yasuhide 
Published: July 2007

AbstractWith a view to increasing the efficiency of the scalar finite element for nonlinear optical channel waveguides, triangular isoparametric elements are introduced. In addition, the numerical integration formula by Hammer et al. is used for the integration needed for deriving the element matrix. The numerical analysis is carried out for the nonlinear optical fibers. It is confirmed that accurate solutions can be obtained by the present method with a small‐size calculation. Also, the analysis of a nonlinear graded channel optical waveguide is carried out for the first time. The effect of the refractive index profile of the substrate on the optical power dependence of the effective index of the guided mode is investigated.
Laminated polarizer with ultrathin germanium for the shorter wavelength with emphasis on modeling the transition layer at the boundaries
Authors: Matsuda Jun‐Ichi , Uchidam Toshiyuki , Kawakami Shojiro 
Published: July 2007

AbstractThe authors have been carrying out research and development of a laminated polarizer (LAMIPOL) as a polarizer suitable of integration. In this paper, with a view to obtain a high‐performance LAMIPOL over a broad, shorter wavelength region (0.6 μm < λ < 1 μm), a LAMIPOL with an ultrathin germanium thin film (20 to 80 Å) was designed and fabricated. As a result, high performance as designed was realized in the wavelength region of 0.6 μm < λ < 1 μm. However, as the Ge laminated layer is made even thinner (such as 20 Å or 30 Å), the computed and measured values for the attenuation constant αTM for the TM wave do not agree and the cause was studied.First, from the experimental results for various Ge thin films, it was found that the nature of the boundary layer does not depend on the lamination thickness of the Ge layer. Further, the model with a boundary layer having a uniform relative permittivity (step approximation) and the model with continuously varying permittivity (linear approximation) were considered. With the latter, it was possible to compute accurately the characteristics of the LAMIPOL for the TM wave if the Ge laminated layer thickness is more than 30 Å.
Observation of internal states of chaos generator with CMOS inverter
Authors: Takakubo Kawori , Takakubo Hajime , Shono Katsufusa 
Published: July 2007

AbstractThe one‐dimensional mapping circuit for chaos generation is constructed using a CMOS source‐follower and a parallel connection of two CMOS inverters. Two one‐dimensional mapping circuits and CMOS switches are used to form a loop to generate the chaos. The initial value is set iteratively by the 12‐bit D‐A converter. The time‐course of the internal state is observed through an A‐D converter with 10‐bit precision. The internal state is determined successively according to the transfer curve of the one‐dimensional mapping circuit. The Lyapunov exponent is determined based on the transition of the internal state near the cycle point.
Optimum design for polarization crosstalk reduction in a polarization maintaining optical fiber of PANDA profile
Authors: Kitamura Fujikazu , Sasaki Yutaka 
Published: July 2007

AbstractThis paper investigates theoretically the polarization‐maintaining optical fiber with a circular stress‐applying part (PANDA fiber) with a high design accuracy and ease of fabrication, with a view to realizing a low crosstalk polarization‐maintaining optical fiber for coherent optical sensing. In general, two orthogonal polarization modes exist in a polarization‐maintaining fiber. Due to the coupling between these two modes, the transmission of a polarized wave is difficult. The infinitesimal polarization component caused by this coupling is called the minor component. The cause of generation of the minor component is confirmed theoretically as the generation of the off‐diagonal term in the relative permittivity tensor. In the past, the off‐diagonal terms have been neglected in the optical fiber in which symmetry is maintained.In this paper, the off‐diagonal terms of the relative permittivity tensor appearing in a PANDA fiber with symmetry are investigated. The effect of the structural characteristics of the PANDA fiber on the crosstalk degradation is analyzed. It is found that the improvement of the polarization crosstalk by 20 to 35 dB is expected with a modal birefringence of less than one‐half the previous case, by making the normalized stress‐applying part half‐spacing 2.83 and the normalized stress‐applying part diameter 0.44.
New reflowable organic spin‐on glass for advanced interlevel dielectric planarization
Authors: Furusawa Takeshi , Homma Yoshio , Shimamura Yasuo , Morishima Hiroyuki , Yamamoto Yasuhiro , Satoh Hidetada 
Published: July 2007

AbstractNew reflowable organic spin‐on glass (SOG) was developed to form planarized multilevel interconnections for ULSIs. This SOG had superior gap‐filling and plan‐arizing characteristics compared to those of conventional organic SOGs. For example, using this SOG, a 0.025‐μm wide trench with an aspect ratio of over 10 could be perfectly filled without void. The surface of a three‐layered interlevel dielectric structure with this SOG was four times smoother than that with a conventional organic SOG.It was found that the excellent gap‐filling planar‐izing property of this SOG was due to the low temperature reflow (100 to 200°C). The film quality was almost the same as that of an organic SOG which has been widely used and has exhibited sufficient reliability. That is, this organic SOG gives a sufficient reliability with far improved gap‐filling and planarization. Since the relative dielectric constant of this SOG is as low as 3.0, this SOG is promising to improve the operation speed of ULSI.
Molecular dynamics simulation of void electromigration under a high‐density electric current stress in an aluminum interconnection
Authors: Shingubara Shoso , Utsunomiya Isao , Fujii Taizo 
Published: July 2007

AbstractThree‐dimensional molecular dynamics simulation of behaviors of a void in an Al interconnection under high current stress has been accomplished employing empirical two‐body potential and the Huntington‐Grone ballistic model for an electron wind force. Stability of a void under a uniform strain field was first investigated; it was shown that a void was stable under a tensile strain, while it was unstable under a compressive strain. Then, a void movement into cathode direction was clearly demonstrated in the single‐crystalline Al interconnection at the high current density of 1 × 1010 A/cm2. The activation energy of the drift velocity of the void was 0.76 eV. Next, behaviors of a void in [111] bicrystal grains with a periodic boundary condition which resembled a bamboo structure interconnection was investigated. A void was stabilized at the grain boundary at low current density conditions; however, it could go across the grain boundary and move further to the cathode direction when the current density was high enough. It was shown that when a void comes close to the grain boundary, it suddenly annihilates into vacancies and rapid movement of vacancies into the grain boundary occur. A void was formed again at the grain boundary. This model will explain the void annihilation phenomena, reported by the in situ scanning electron microscope (SEM) observations. After stopping the current, a backflow of a void was observed as a consequence of the strain energy relaxation when the current density was high. These obtained results explained well the experimental observations qualitatively; furthermore, new predictions were obtained with quantitative analysis based on total potential energy analysis.
A new very fast pull‐in phase‐locked loop with antipseudo‐lock function
Authors: Shirahama Hiroyuki , Taniguchi Kenji , Nakashi Kenichi 
Published: July 2007

AbstractWith the development of high‐speed digital communications, e.g., optical fiber communications, smaller, faster, retiming devices are being required. The phase‐locked loops (PLLs) are suited to an integration compared to surface acoustic wave (SAW) or liquid crystal (LC) passive filters. Therefore, PLLs have been put to use gradually as clock extraction devices in any frequency range over 100 MHz. The authors have developed the previously reported PLL with frequency difference detector (FDD) to provide a new function, which is useful to overcome the pseudo‐lock problem in conventional retiming PLLs and also improved performance of the FDD. The proposed PLL has been constructed with ECL‐IC, PLA and other discrete parts. It has been evaluated experimentally and the PLL designed with a 0.8‐μ design‐rule bipolar transistor has been evaluated by simulation to confirm the following characteristics.1. The PLL can detect an initial unlock state and pseudo‐lock state within almost the same time as FDD sampling time and can recover rapidly.2. The jitter transfer function is almost equal to the usual first‐order PLL and is independent of input data patterns.3. The FDD frequency detecting range, corresponding to the PLL lock‐in range, is more than four times that of the previously proposed FDD‐PLL.
Detection of the complex amplitude distribution of a kinoform using an iterative fourier‐transform algorithm
Authors: Akahori Hiroshi 
Published: July 2007

AbstractThis paper presents a method for recovering, by using the iterative Fourier‐transform algorithm, the complex amplitude transmittance of a recorded one‐dimensional Fourier transform‐type kinoform. A method for estimating the phase‐recording characteristic of the kinoform fabrication system by comparing the retrieved phase with the theoretical phase is also presented. The spatial variations of both the magnitude and phase inside each of the kinoform cells were evaluated to improve estimation of the phase‐recording characteristic. The initial estimate of the kinoform phase given to the algorithm was derived using the knowledge that the recorded phase is an approximation of the phase to be recorded.The relationship between the shift of the central sampling point of the Fourier image from the optical axis and the retrieved phase of the kinoform is investigated; a kinoform phase pattern with a structure suitable for indirectly detecting the shift is then proposed. In an experiment using a kinoform fabrication system including a photographic process, the recorded phase distribution is retrieved at five sampling points of each cell. The phase‐recording characteristic is estimated using the retrieved phase values.Next, a computer simulation is executed to reveal the influence of errors in the measurement of magnitude. The simulation result shows that the recorded phase distribution can approximately be retrieved when the rms error added to the magnitude is approximately 10 percent of its average. Furthermore, the validity of the phase distribution retrieved in the experiment is discussed.
Optimum design technique for optoelectronic devices using simulated annealing
Authors: Hara Kunihiko , Iwamoto Takashi , Kyuma Kazuo 
Published: July 2007

AbstractA new procedure for the optimum design of optoelectronic devices is explained in this paper and an automatic search is made simultaneously for the structure satisfying various demands. The feature of this procedure is in the introduction of cost by which the quantitative evaluation of the structure becomes possible and the global search for the required structure by simulated annealing can be carried out.First, the definition of cost and details of the optimization procedure are clarified. In optimization, in addition to convergence to the minimum point of the cost function (the optimum configuration from theoretical viewpoint), the convergence also is possible in structures with great tolerance to fabrication errors (neighborhood cost (NC) and finite temperature annealing (FTA) methods).Next, these three proposed methods are used in the design of a pnpn differential optical switch and the effectiveness of the methods is verified. The method of cost expression, the relation between annealing parameters, and convergence are investigated. It is shown that cost expression with large degree of freedom improves the search for high‐performance structures and the initial temperature of annealing or the fixed temperature of FTA method is the important parameter which sets up the probability of acceptance. Further, it is shown that the convergence cost is inversely proportional to the time spent in annealing. These results are useful guidelines in the optimum design of arbitrary optoelectronic devices.
Multilevel interconnection technology without via‐hole mask (maskless pillar process)
Authors: Ueda Tetsuya , Yano Kousaku 
Published: July 2007

AbstractRecently, with the miniaturization of ULSI patterns, the percentage of the LSI production cost occupied by the multilevel interconnection process is increasing due to the increase in the process steps and the introduction of new materials. In order to realize miniaturization process and achieve cost reduction at the same time, via‐hole maskless multilevel interconnect technology (mask‐less pillar process) has been developed. By merging the via‐hole mask information on the underlying interconnection mask and by a selective etching of the multilevel metal films which depends on the mask width, underlying interconnection and metal pillars are formed simultaneously. The reduction of process steps has become possible by eliminating the via‐hole lithography, etching, and filling process. As a result of electrical measurement of samples formed by the maskless pillar process, the feasibility for two‐level metal interconnection has been verified, which confirmed it to be a multilevel interconnection process suitable for sub‐half micron devices with guaranteed reliability.
Tuning and wideband intensity modulation of noncollinear quasi‐phase‐matched second‐harmonic generation using pockels effect
Authors: Koyanagi Kojiro , Mishima Teruhito , Sakuraba Ichiro 
Published: July 2007

AbstractThe difficulty in highly efficient quasi‐phase‐matched second‐harmonic generation (QPM‐SHG) using periodic nonlinear structures is the strictness of the allowance of the period length or the fundamental wavelength in the quasi‐phase matched condition. As a result of these difficulties, the increase of the allowance and the easy fine‐tuning of quasi‐phase matching are very important. In this paper, the fine‐tuning of the quasi‐phase‐matched condition in bulk noncollinear (two‐dimensional) QPM‐SHG by adjusting the angle of incidence of the fundamental wave and by using the Pockels effects by the applied electric field is proposed and its properties are investigated theoretically. For wavelength variations of the fundamental wave, relaxed allowance by automatic readjustment of the angle of incidence using angular dispersions of a diffraction grating is also proposed. The relaxation is adopted in light‐intensity modulation of bulk‐type noncollinear QPM‐SHG, which is achieved by variations in phase‐matched condition by electro‐optic effect. Because nonlinear material, periodic domain inverted LiNbO3 is assumed and tuning, relaxation, and modulation characteristics are investigated through numerical simulations. As a result, it is shown that rapid tuning can easily be achieved and the proposed wide wavelength‐band light intensity modulator is expected to realize applications in optical disks, etc.
Complex permittivity measurement of dielectric materials using nonradiative dielectric guide at millimeter wavelength
Authors: Ishikawa Youhei , Tanizaki Tohru , Saitoh Atsushi , Yoneyama Tsukasa 
Published: July 2007

AbstractIn this paper, as a method for measurement of complex permittivity of millimeter‐wave dielectric materials, a transmission resonator method is proposed which is made of a dielectric resonator with both sides open placed in a nonradiative dielectric (NRD) guide. For the evaluation of the surface resistance of the conductor indispensable for measurement of the complex permittivity, a pair of TEoml mode resonators are placed coaxially and are mutually coupled. The difference of the conductor losses for the even and odd mode resonances of this resonator system is detected as the difference of the unloaded Q's so that the surface resistance is derived.The special features of the present measurement method are to evaluate the conductor surface resistance at a high sensitivity in a condition close to the resonator with both ends short‐circuited and to use a resonator with both ends open‐circuited for sample measurement because the effect of the surface resistance is small so that high accuracy is obtained as a whole. By using an NRD guide excitation method, a measurement system is realized which affects very little the unloaded Q of the resonator system and the electromagnetic field distribution.For the calculations of the complex permittivity, the eigenvalue calculation by the finite element method and the perturbation method by Kajfez are combined. For the samples with its relative permittivity of 24 and the loss tangent of 2 × 10−4, the measurement fluctuations are less than 0.005 percent for the resonant frequency and less than 1 percent for the unloaded Q. The measurement accuracy for the relative permittivity is less than 0.4 percent and that for the loss tangent is less than 3 percent.