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Waveguides Finite Difference Time Domain Method In The Calculation

Posted on:2001-07-24Degree:MasterType:Thesis
Country:ChinaCandidate:Z Q HuangFull Text:PDF
GTID:2208360002951375Subject:Circuits and Systems
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Finite-difference time-domain method is a numerical calculation method of finding the solution to the electromagnetic field in the time-domain It transfers Maxwell Differential Equations vith time variant to difference equation so as to find the solution to each of eleclromagnetic field. Since the foundation of FD-TD method, it is mainly used in researching the effect of common electromagnetic waves on various objects. However, there are still few reports of the application in the research of optical field. Analytic method was generally used to research the optical wave-guide, and was limited in the research of regular-structured wave-guide devices. As to the irregular- structured wave-guide devices, the analytic method is incapable of solving the problems. With the development of optical wave devices, many kinds of sophisticated optical wave- guides have appeared since 1980's. The accurate solution to the boundaiy value of electromagnetic field can provide a theoretical foundation for the excellence and design of optical waveguide, it is hard to find an accurate analytic solution, thus a numerical calculation method is requirecL Numerical calculation methods other than FD-TD method have limitation. The FD-TD method is directly perceived, rapid, simple in procedure, commonly used. It saves space and time of calculation and has clear data and pictures. This thesis introduces this method to the calculation of optical field in the optical wave- guides. It has arrived at the same conclusions vith the analytic method in many documents, thus proved the feasibility and efficiency of FD-TD method in the researches of optical fields. This thesis first analyzes the distributions of mode fields of TE0 and TE1, TE2 of Plane wave-guides and graded-index wave-guides in two-dimensional scalar and vector FD-TD methods. The results are that the pictures are almost the same in the two methods, but the scalar FD-TD method is more simple, convenient, saving thne and the vector FD-TD 3 method is more accurate. To analyze common plane wave-guides and graded-index wave- guides, the two-dimensional scalar FD-TD method is required. To analyze complicated wave-guides, the vector FD-TD method is compulsory When the vector FD-TD method is used, half steps of the meshes appear. Previous documents usually use the method of transferring the field value of half steps of the meshes to integer steps of the meshes. an average method is used in this thesis. It need not transfer the meshes to eliminate half steps of the meshes. Furthermore, five kinds of optical sources are used as stimuli, they are plane optical source, Guassian optical source, spherical optical source, SIN* SIN optical source and SIN*COS optical source. The concluded distributions of optical fields after the stabilization of the spreading of optical fields are identical with the results in the analytic method. It indicates that the distributions of the stable optical fields have nothing to do with the stimulated optical sources and the analytic methods. The distributions are just connected with the structural parameters of the optical waveguide and the optical wavelength. This thesis also discusses the TB0 field distribution of the channel wave-guide by the three-dimensional FD-TD method. The result is identical with that in the analytic method. It further proves the wide applications of the finite-difference time-domain method in the calculation of optical wave-guides.
Keywords/Search Tags:optical wave-guide, finite-difference time-domain method, mode field distribution, scalar FD-TD method, vector FD-TD method
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