摘要:

AbstractSmall‐sized, high‐speed optical scanners are very useful in optical information processing, optical communications, optical measurements, etc. Although there has been research on various devices of this kind, satisfactory characteristics are yet to be realized.This paper proposes a guided‐type optical scanner in which the propagation constant of each waveguide is varied independently by electronic means, and its characteristics are simulated. It is found that the number of resolvable spots is proportional to the number of waveguides and more than 670 resolvable spots can be obtained for the case of 1000 waveguides. Further, the number of resolvable spots is not influenced much even if phase errors of about 1 percent (2π/100) are introduced in each waveguide. Moreover, it is clarified that the coupling coefficient between the waveguides must be kept below 100 m−1for the device length of 1 mm, and several other points are e

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper presents a new coupled‐mode theory by extending Chuang's theory to include the radiation modes. The effectiveness of this theory is demonstrated via numerical analysis.The coupling equations are derived following a procedure similar to Chuang's and the radiation modes are included in it. The coupling equations are simplified by neglecting the terms which represent the coupling between the radiation modes because their contribution is insignificant.In the numerical analysis, the radiation modes are treated in isolation and the coupling between them is neglected. The model for the numerical analysis is that of a symmetrical and asymmetrical optical slab waveguide. The light intensity distribution inside the guide is investigated numerically and the results are compared with those by Chuang's theory.As the result of analysis, it is shown that due to excitation of radiation modes near the input/output end, the coupling length estimated by the present theory is longer than that by Chuang's theory. Moreover, the light intensity distribution has been extende

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe electromagnetic waves propagating along an open waveguide can be classified in several ways. For instance: (1) guided modes and leaky modes; (2) real modes and complex modes; and (3) proper modes and improper modes. However, their mutual relationships are not clear. In addition, the physical meaning of the leaky mode is not well understood in comparison with the guided mode.In this paper, the relationship of the modes propagating in a dielectric slab waveguide is investigated. First, from the dispersion equation, the guided mode cutoff frequency and the leaky mode cutoff frequency are obtained so that the regions of the guided mode and the leaky mode are found. It is shown also that there exists an improper mode region with real propagation constants between the guide and leaky mode regions.This improper mode does not decay in the direction of propagation and the amplitude increases away from the waveguide along a straight line with an arbitrary angle from the propagation direction. In this region, the group velocity may exceed the speed of light in free space or become infinite. Thus, in this paper, this region is called the anomalous group velocity region. The width of this region is inversely proportional to the mode number and the waveguide width.

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIn the computer‐generated double‐phase hologram, parity noise appears in the image. It is desirable to form the computer‐generated hologram with fewer subcells as fabrication is easier. With a view to eliminating the parity noise of the computer‐generated double‐phase hologram, this paper presents a method in which the information canceling the parity term itself is provided at the center of the cell of the hologram so that a better image is obtained. By means of the theory, computer simulation and optical experiments, the method is prov

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe full‐wave analysis methods in the time domain including the finite‐difference time‐domain method are promising as general‐purpose analysis techniques for three‐dimensional structures. They have been applied extensively to microstrip line circuits; and, in this paper, they are extended to coplanar line circuits and the finite‐difference time‐domain method is applied to the analysis of coplanar lines considered important as the configuration element for uniplanar monolithic microwave integrated circuits (MMIC).The analysis results are presented for the transmission line parameters of the coplanar waveguides and coplanar strips, models for open ends and short‐circuited ends, characteristics of the T‐junction and the effect of the air bridges. Using these analyses, the possibility of applications is proven. In addition, the points to be noted and future subjects are studied so that the method can be extended as a tool for the

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractSince the problem of waveform distortion in optical communications can be overcome by optical soliton, very wide band transmission becomes possible. It is foreseen that soliton propagation is the candidate for future optical systems. The soliton behavior can be expressed by the coupled nonlinear Schrödinger equations.In this equation, taking the nonlinear oscillatory or loss terms due to the mutual parametric effects of each polarization component into account, the analysis will become very complicated. Concerning this point, in most analytical procedures, such oscillatory terms are neglected. However, the contribution of these terms are large in optical fibers of low birefringence and, therefore, they cannot be neglected.In order to establish a unified and effective approach, taking these perturbation and oscillatory terms into account, an analytical procedure based on the finite element method is proposed. Ultrashort pulse transmission in various fibers and the effects of the birefringence upon soliton pulses are investigated. The correctness of the present method is verified and several new results are obtained. Finally, in case of subpicosecond pulse transmission in optical fibers of low birefringence, it is shown that the contribution of the above mentioned terms is quite remarkable

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractThe deposition condition of rf‐sputtered tungsten with low stress for an X‐ray absorber and the mechanism of the stress in the film will be described. The stress in the film becomes compressive or tensile, depending on Ar pressure during sputtering. The stress behavior can be explained by the lattice expansion due to the incorporation of Ar, the columnar film structure, and the change of the crystalline structure.Low stress films suitable for an X‐ray mask absorber can be reproduced by thermally treating a β‐W which is deposited under Ar pressure below 35 mtorr, at temperatures bel

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractAs analog ICs are finding use in a higher frequency band, a circuit simulator which is accurate in a high‐frequency region beyond 100 MHz becomes necessary. In this paper, a 600‐MHz wideband amplifier IC and its bipolar transistors and resistors are fabricated on an identical chip. By evaluating theirSparameters, the accuracy of the device model was verified for simulation of analog IC at frequencies above 100 MHz.First, the parasitics of packages were modeled to verify the accuracy of the device model. It is shown that consideration of the resistance of pads is necessary. Next, the accuracy of the hybrid π model used widely as a high‐frequency model of the bipolar transistor was verified with theSparameters. It is found that the present form has poor accuracy at frequencies above 100 MHz. It is shown also that the IC structure of the transistor must be considered to improve the accuracy.Significant improvement of accuracy can be obtained if an extended model is introduced in which the separations of the base‐collector capacitance and the base‐emitter capacitance and the introduction of substrate resistance are included. Finally, by means of this extended model, a good high‐frequency simulation of a 600‐MHz wideband amplifier

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractHigh‐density DRAMs have become susceptible to small defects as their fabrication process becomes more complicated, i.e. smaller transistors, thinner dielectric films of memory cell capacitors and three‐dimensional memory cells. Therefore, it is necessary to establish a test method that strictly screens latent defective devices derived from the fabrication process in a short time.Discussions about the defect modes during burn‐in tests indicate that recent high‐density DRAMs employing a 1/2‐VCCcell plate scheme exhibit slower convergence of initial defects in memory cell dielectric capacitor films than in metal wiring layers during burn‐in tests. To overcome this problem, a new operation mode (aging mode) that switches the cell plate voltage toVCCorVSSduring burn‐in tests is proposed.In this aging mode, we can accelerate the aging process by putting sufficient electric field to capacitor dielectric films without applying excessive stress to normal devices. Good convergence of defective devices in a short time due to this aging mode by experimenting with burn‐in tests for the test devices havingVSScell plate capacitor dielectric films of 100 Å has been confirmed, and this aging mode on 4MDRAM devices has

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY

摘要:

AbstractIt is important to measure the refractive index profile in an optical waveguide. In particular, there has been a demand for the development of simple methods to measure precisely the refractive index profile in a waveguide with a small number of propagation modes. One of the methods which can provide relatively high resolution is the edge reflection method using an optical fiber as a probe. This method has been used to evaluate a rod lens.In this study, the edge reflection method was used to evaluate a diffused‐type glass waveguide with small dimensions. To increase the sensitivity to reflected light, the fibers for incident light and reflected light detection were located with a certain angle, that is, an oblique incident light system was used. In addition, to increase the spatial resolution, the refractive index profile in the direction of interest was expanded by angle lapping of the edge of the test fiber. By using this method, it was possible to measure easily the refractive index profile in a silver‐diffused glass optical waveguide with two propagating mo

ISSN:8756-663X    

DOI:10.1002/ecjb.4420731110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1990

数据来源: WILEY