bluuebunny/crossref_metadata_2025_split huggingface dataset:
Uniform asymptotic solution of guided modes in inhomogeneous slab waveguides with an even polynomial refractive index profile
Authors: Yata Akira , Ikuno Hiroyoshi 
Published: July 2007

AbstractUniform asymptotic solutions are obtained for the propagation constants and field distributions for guided modes inside slab waveguides with inhomogeneous profiles of refractive index. Uniform asymptotic solutions are formed with an arbitrary order by a recursive algorithm for a related equation method. Through a quantum condition the propagation constant is determined. The parabolic cylinder functions describe the field distributions. By the expansion coefficients of polynomials which approximately represent the refractive index profiles, the asymptotic solutions can be represented analytically. This paper examines the analytic solution for a squared hyperbolic tangent profile, and for a Gaussian profile, it was analyzed numerically. The effectiveness of the uniform asymptotic solutions was verified.
Optical scanning image sensor
Authors: Yamada Satoru , Sakai Syunji , Iguchi Yasuo , Sakamoto Masaaki 
Published: July 2007

AbstractAs an image input device such as a facsimile and an image scanner, various image sensors have been studied. This paper describes an optical scanning contact image sensor as a form of contact image sensor. In the optical scanning type, the dots of the LED array used as a light source are activated one by one and a text is illuminated via a rod lens. The reflected light is converted to electrical signals by one photo‐detector. This system has the advantage of an extremely small power consumption. In the present trial fabrication, an a‐Si photodetector (with a pin structure) with one long element of 128 × 0.5 mm and reading width of the text 122 mm is employed. As a result, the power consumption of the present image sensor is 0.25 W (power supply voltage of 5 V) including the illumination.
Finite‐element formulation in terms of the magnetic‐field vector for axially symmetrical graded‐core optical fibers
Authors: Kumagami Hiroshi , Hayata Kazuya , Koshiba Masanori 
Published: July 2007

AbstractA finite‐element method for the analysis of axially symmetrical graded‐core optical fibers is formulated in terms of all three components of the magnetic field. By considering the axial symmetry of optical fibers, the inhomogeneous core region to which the finite‐element method is applied is divided into axially symmetrical ring elements and the homogeneous cladding region is treated analytically. Therefore, very accurate results can be obtained even for near cutoff. Also, for elimination of spurious solutions, the penalty method, the transverse magnetic‐field method, and the Kobelansky‐Webb method, which have been developed for the finite‐element analysis of axially nonsymmetrical waveguides, are introduced. Then the accuracy of finite‐element solutions is investigated in detail from the viewpoint of the order of elements and the treatment of refractive index distribution within each element. To check the validity and usefulness of the method proposed herein, a step‐core optical fiber and a graded‐core optical fiber are analyzed, and the results obtained are compared with the exact solutions and the results of the power series expansion method.
Reflection and transmission characteristics of rectangular dielectric waveguide junction with transverse displacement
Authors: Tomabechi Yoshiro , Matsumura Kazuhito 
Published: July 2007

AbstractIn the case where rectangular dielectric waveguides with identical cross sections and relative permittivity are connected with a lateral offset, the reflection and transmission coefficients of the guided mode in this portion are calculated and the radiation power is obtained. First, the boundary condition to be satisfied by the electromagnetic field in the junction plane (perpendicular to the direction of propagation) at the offset junction is determined. Next, a double Fourier transform is applied to this boundary condition and the latter is solved in the spectral domain. The reflection and transmission coefficients thus obtained are used as the first‐order approximation and the parameters corresponding to the phase constants introduced separately in the spectral domain are corrected successively. By means of this approach, the reflection and transmission coefficients of the guided mode can be converged to constant values. The reflection and transmission coefficients obtained in this manner are used for calculation of the radiated power generated at the offset discontinuity. It is confirmed that the energy conservation law holds almost at this offset junction. Hence, the numerical accuracy is believed sufficient. A portion of the results was compared with the experimental data and good agreement was found. The present analysis method is believed to be useful for such integrated circuit design as calculation of the allowable offset values in an optical communication system in which rectangular dielectric waveguides are connected with offset.
Ridge‐shaped narrow‐wall directional coupler. Tight coupling and high‐power handling capability
Authors: Tanaka Toshiaki , Aikawa Masayoshi 
Published: July 2007

AbstractA new ridge‐shaped narrow‐wall directional coupler is proposed which can realize a tight coupling and a high‐power handling capability. In the proposed coupler, the right‐angled corners of the coupling slot of the conventional ridge‐shaped directional coupler are rounded off so that a tight coupling characteristic can be obtained in a broad frequency range. The new structure preserves the features of the conventional ridge‐shaped coupler, that is: (1) flexibility of the spatial arrangement of the two coupling waveguides, and (2) the possibility as a variable power divider. The boundary element method has been used for the electromagnetic analysis.The obtained performances are such that the coupling is 1.5±0.5 dB, the return loss is more than 20 dB, and the isolation is more than 20 dB in the frequency range of 27 to 33 GHz. The measured coupling characteristics agree well with the computed results.
Properties of optical retardation plates by easily prepared birefringent bulk plastics
Authors: Muto Shinzo , Ichikawa Akio , Okuda Ken‐Ichi , Kawai Masato , Ito Hiroshi 
Published: July 2007

AbstractWhen a dc electric field is applied to molten polystyrene and α‐methylstyrene, the molecules are aligned in the direction of the electric field. Since this state is maintained even in a solid state, birefringent bulk plastics are easily obtained. The merit of this technique is that the magnitude of birefringence is contained by controlling the dc electric field. Since there is no size limitation, λ/4 and λ/2 plates were obtained easily at low cost. Furthermore, these optical retardation plates can be used for a wide range of wavelengths. It was found that the temperature dependence of the optical properties does not cause problems at normal usage temperatures.
Insertion force reduction in multipin connectors with various tip shapes
Authors: Yasuda Kei‐Ichi , Nakano Kenichi , Kanai Tsuneo , Ando Yasuhiro 
Published: July 2007

AbstractTo decrease the insertion force of multipin electrical connectors in communication equipment, the tip shape of the male connector was analyzed theoretically, and a model experiment of contact insertion was carried out. From comparison of the theoretical and experimental results, the following results were obtained: (1) if the friction between contacts in connector insertion is not taken into account, a root curve shape is the optimum tip shape; and (2) the insertion experiment using a model for a male connector tip agrees with the theoretical result. As a result, it was shown that the friction between the contacts has an important role, and that to reduce the insertion force, the shape of the tip must be designed with friction taken into account.From the foregoing results, the connector tip was designed to make the insertion force constant regardless of friction. By investigating the force reduction using a multipin connector of about 200 pins, the evaluation based on the tip shape was found to be valid.
Slot—coupled directional couplers on a both—sided substrate MIC and their applications
Authors: Tanaka Toshiaki , Tsunoda Kikuo , Aikawa Masayoshi 
Published: July 2007

AbstractA slot‐coupled directional coupler is proposed and analyzed. In the slot‐coupled directional coupler, microstrip lines set on both sides of a common ground plane are coupled through a slot in the common ground plane. This coupler can easily realize a tight coupling such as 3 dB with a small physical size. This paper shows that it is possible to form a planar multiport directional coupler with 2n (n: integer) input or output ports without line crossings by combining slot‐coupled directional couplers. Using such a planar multiport slot‐coupled directional coupler, a multiport power amplifier and a BMN (Butler matrix network) can easily be formed in a small physical size.The 3‐dB slot‐coupled directional coupler fabricated for trial has a coupling of 3.2 ± 0.2 dB, a return loss of more than 25 dB, and an isolation of more than 28 dB in the frequency range of fO ±20 percent (fO = 1.5 GHz). These measured values agreed well with computed data.
Vectorial finite—element formalism for electromagnetic waveguiding structures with loss and/or gain
Authors: Hayata Kazuya , Miura Kazunori , Koshiba Masanori 
Published: July 2007

AbstractTo carry out a vectorial wave analysis of the eigenmode in an electromagnetic wave‐guiding structure with loss or gain, an efficient vector finite‐element expression is derived based on the finite‐element method in terms of the transverse magnetic field component. Since the eigenvalue of the final matrix equation corresponds to the propagation constant, it is possible to obtain the propagation constant for a given frequency. Hence, it is possible to avoid inefficient iterative calculations on a complex plane which have been used in a conventional method in which the frequency is used as an eigenvalue. Also, the present method can be applied to a dispersive medium in which the medium constant is dependent on frequency and to a structure containing a conductive material in which the loss tangent varies in proportion to the inverse of frequency. From these properties, the present method is believed to be a practical numerical method for the vectorial analysis of guided wave structures containing loss or gain. To confirm the validity of the method, some analytical results are presented for a rectangular waveguide loaded with a lossy dielectric material. Convergence of the solution is checked and the result is compared with the exact solution. Next, as a more interesting example, guided mode analyses are performed for buried heterostructure semiconductor lasers and lossy coupled dielectric waveguides and the results obtained are discussed.
Two—dimensional ray tracing for wavefronts, wave—normal rays and geometrical optics fields
Authors: Hashimoto Masahiro , Komiyama Akira 
Published: July 2007

AbstractA method is described for constructing geometrically the two‐dimensional electromagnetic wave in an inhomogeneous anisotropic medium. An example of application is also shown. Since the basic theory has already been reported, an application algorithm is described here in detail. Especially, the geometrical optics field at an arbitrary time is traced numerically after the initial shape of the wavefront and the initial intensity profile of the electromagnetic field are given. In the example, a uniaxial anisotropic medium with a weak inhomogeneity is assumed and the initial intensity profile of the geometrical optics field is taken Gaussian.
Transient analysis of three—dimensional electromagnetic field in through—holes
Authors: Masuzuka Naoki , Yoshida Norinobu , Fukai Ichiro 
Published: July 2007

AbstractThrough‐holes are attached to numerous structures in mutual connections of electronic devices, printed circuit boards which provide supporting functions, multilayer wires of LSI, and external connections of IC packages. With the recent uses in superhigh‐frequency waves in superminiaturized circuits, the influences of through‐holes on the propagation characteristics are becoming increasingly nonnegligible. To understand the characteristics of the total system, analyses of through‐holes have become indispensable. However, through‐holes generate complicated distributions of electromagnetic fields due to their three‐dimensional structures. Thus, it is necessary to perform rigorous vectorial analyses for three‐dimensional fields using all field components, boundary conditions, and properties of the medium.Hence, for analysis of through‐holes, we applied the method of spatial networks. These networks have many features for analyses of electromagnetic fields in obtaining time responses of the three‐dimensional fields. We simulated their basic field behaviors, and obtained transmitted output waves which provide an important influence of a through‐hole on characteristics of high‐speed pulse operations and reflected wave shapes toward the input terminals. We determined the frequency characteristics of those wave shapes by fast Fourier transforms, and clarified the effectiveness of the application of the present analysis method.
Analysis of a bending dielectric slab waveguide by integral equation formulation
Authors: Matsuhara Masanori , Toyoda Ichihiko , Shirae Hisazumi 
Published: July 2007

AbstractThe waveguide bend is an indispensable circuit element in realizing optical integrated circuits. In this paper, the bend in a dielectric slab waveguide is analyzed numerically by means of the integral equation formulation. When a numerical solution of an integral equation is attempted by the boundary‐element method, two problems exist: 1) how one can connect the field distributions expressed by the boundary‐element method with those by the eigenmodes of the waveguide. In this paper, instead of representing the field at the input/output boundary of the bend in the slab waveguide in terms of the boundary‐element method, a new method is proposed in which the field distributions expressed in terms of the eigenmodes are substituted directly into the integral equation; and 2) the treatment of the radiation mode. In this paper, a discretization method based on the sampling theorem is used. As an example, numerical calculations have been carried out for a conventional bend and a reflection bend in a dielectric slab waveguide. It is confirmed that the results agree well with data obtained by other methods. It is pointed out that good results can be obtained for such cases as a structure with large difference in index of refraction between the core and cladding and the one with a large bend angle, which were difficult to analyze by the conventional methods. Further, it is shown that the bending loss of the reflection bend is substantially smaller than that of the conventional bend.
Three‐dimensional analysis of electromagnetic fields for NRD guide with air gap and finite‐metal plane width
Authors: Terashima Kouji , Yoshida Norinobu , Fukai Ichiro 
Published: July 2007

AbstractActive researches have been conducted recently on NRD lines which have low loss properties in millimeter wavebands and are suitable for integrated circuits. As an example for them, an asymmetrical structure has been proposed for an NRD guide which may be used for a leaky wave antenna. This paper analyzed such a guide for its three‐dimensional spatial‐time responses based on the Bergeron method. We made vectorial analyses on the instantaneous waveforms for all components of the electromagnetic fields and applied Fourier transform on the instantaneous waveforms in the spatial domain. From the wave number spectra thus obtained, we identified the existence of two leaky waveforms for individual modes. We obtained the propagation constant for each mode. Based on characteristic variations of the propagation constant for the dominant leaky mode as a function of the width of a longitudinal conducting plate and on the Poynting vectors, we showed that an NRD guide of such geometry becomes a leaky wave antenna.
Analysis of transmission characteristics of image fiber‐dependence on higher modes and wavelength
Authors: Yamaguchi Shoji , Shimojima Akira , Hosono Toshio 
Published: July 2007

AbstractIn transmission by image fiber, the image is blurred by mode coupling due to the crosstalk cores, which impairs the resolution. The analysis of such crosstalk phenomena by geometrical optics is very difficult, and wave theory must be employed. There are infinite modes excited in each element fiber of the image fiber. In case of low resolution, that is, when the period of spatial harmonics of the image is small compared with the size of element fiber, higher modes are excited in the fiber.In this paper, the effects of higher modes upon image transmission characteristics of one‐dimensional image fiber are analyzed using vector wave theory. Since the crosstalk characteristics vary widely with wavelength, and various wavelength components are involved in the input image, the analysis of wavelength dependency of the crosstalk is important. By the numerical method, various characteristics are analyzed, and improvement methods are also discussed.
Study of contact phenomena in the vaporized organic gas atmosphere
Authors: Yoshida Kazuhisa , Motoyama Akira , Isagawa Mitsuo , Miyazaki Youichi 
Published: July 2007

AbstractIn the vaporized organic gas atmosphere, the bridge duration and the switching characteristics of a communication relay under the bridge load (DC10 V, 10 mA) were evaluated. As a result, it was found that the bridge voltage waveform pattern changes because of a carbonized product, the bridge voltage (2 ∼ 4 V), which is higher than the boiling voltage of the contact metal (0.9 V), appears, and the actual bridge duration is about 10 times longer than the bridge duration of the contact metal (1 ∼ 5 μs). When the minimum bridge duration is longer than 10 μs, the probability that the contact resistance is higher than 100 mω is over 75 percent.The timing of the bridge duration increase depends on the kind of organic gas used. When the organic gas has a high degree of polymerization, the bridge duration should be used as an evaluation parameter because the timing of the increase in the bridge duration and contact resistance are accelerated. Using these concepts, the contact phenomena and degradation mechanism of a relay in the bridge load region in an atmosphere of volatile organic gas has been clarified.
GaAs‐ALGaAs double‐heterostructure coupled‐waveguide optical modulators and their high‐frequency modulation characteristics
Authors: Tada Kunio , Hayashi Hideki , Kawanishi Satoki 
Published: July 2007

AbstractIn this paper, a GaAs‐AlGaAs double‐heterostructure (DH) coupled‐waveguide optical modulator, which is important as a multifunction optical component and for possible monolithic integration, has been studied in detail. A DH device with pn‐junction structure, which is expected to have the lowest switching voltage, has been fabricated and the optical modulation characteristics have been measured at 1.06 μm wavelength. At a reverse bias of 13 V, an extinction ratio of 11 dB has been obtained. However, the cutoff frequency has been limited to about 250 MHz, which was lower than the calculated value of 1.1 GHz obtained using a simple lumped‐element circuit analysis. Therefore, the optical modulation characteristics have been analyzed assuming the device as a distributed‐element circuit line, and also taking into account the external parasitic impedancees. Thus it has been concluded that a reduction of the top‐electrode resistance and an increase of the conductance across the device cross‐section are necessary to improve the high‐frequency optical modulation characteristics.To verify these results, a DH Schottky contact structure, which essentially possesses no ohmic contact resistance with a thick topelectrode, has been fabricated on a MBE‐grown wafer. At a reverse bias of 16 V, an extinction ratio of 12 dB and a cut‐off frequency of 1.5 GHz have been obtained successfully. It has also been concluded that an even thicker top‐electrode and an improved mounting method which minimizes the external parasitic elements are necessary for further improvement of the optical modulation frequency characteristics.
Automatic measurement for investigation on the contact surface using nonlinear characteristics
Authors: Minowa Isao , Kanno Makoto 
Published: July 2007

AbstractTo improve the reliability of an electrical signal transmission through a contact, not only the contact resistance, but also the nonlinear characteristic must be evaluated, especially in the presence of a surface film. This method is effective in the separation of the film resistance and the constriction resistance, and the measurement of film thickness. To investigate the distribution of the oxide film thickness, the system was fully automated to measure the film thickness at various points on a sample surface. The measured properties were the contact resistance and the dc current which is one of the nonlinear components and is needed to cancel the rectification characteristic. To form a contact, copper, platinum and nickel wires were used. This paper demonstrates three‐dimen‐sionally and statistically the characteristics at various spots on a plane.
Boundary‐element analysis of plane‐wave diffraction from metallic gratings with arbitrary complex permittivity
Authors: Nakata Yasunori , Koshiba Masanori 
Published: July 2007

AbstractFor the problem of plane‐wave diffraction from metallic gratings with arbitrary complex permittivity, a new analysis method based on the boundary‐element method is proposed. First, this diffraction problem is analyzed by the boundary‐element method as a two‐media boundary value problem taking into consideration the metallic loss. Further, a simple method is proposed in which an approximate boundary condition using the surface impedance is incorporated into the discretized equation by the boundary‐element method. Especially, in the method using the surface impedance approximation, the region to be analyzed is reduced to only the incident side so that efficiency of both the formulation and the numerical calculation can be improved significantly. The diffraction characteristics of the sinusoidal grating and the Fourier grating were actually computed. The results were compared with those by other methods and by experiments so that the validity and usefulness of the present method are confirmed.
Fabrication of a micropump for integrated chemical analyzing systems
Authors: Shoji Shuichi , Esashi Masayoshi 
Published: July 2007

AbstractUtilizing micromachining based on the semiconductor device fabrication technique, a miniature pump (micropump) was fabricated on a silicon substrate. The purpose of this study is to integrate a conventional chemical analyzing system on an Si substrate by using microchemical sensors such as ISFET's and microvalves. The micropump was the diaphragm type. The pump was composed of an inlet and outlet having a one‐way microvalve, a pressure chamber formed on an Si substrate and a miniature piezoactuator. The size of the pump was 8 mm x 10 mm x 10 mm and the flow rate on the order of μl/min could easily be controlled by the voltage signal applied to the actuator. To monitor the flow of the pump, a differential pressure sensor which could be formed on the Si substrate was developed. The sensor was composed of a oneway valve and a piezoresistive diaphragm‐type pressure sensor, and had a high sensitivity to small flow.