Abstract
AbstractAs far as the quantitative analyses of propagation constants are concerned, the corresponding index profiles, encountered in the real world, are too complicated which makes the exact results of the propagation constants in the wave-guiding structures unlikely. To handle this basic problem, we should resort to some kinds of approximations, either from physic or from mathematic points of view.In this thesis, we apply an approximation method, which has a closed-form expression. The closed-form expression tells the relationship between the two propagation constants in each of two different waveguides. To check how good this approach is, we compare our approximate results with the exact values, if available. In our presented examples, we find that the discrepancies between the exact and the approximate results are rather small, to lie in between 0.002% and 0.0005%. In other words, the closed-form expression for quantitatively estimating propagation constants in wave-guiding structures is likely good, thereby possibly being universal in the problems addressed above. To get a closer result, we also introduce an iterative approach in this thesis as well.