A plane-wave boundary method is proposed for the analysis of bent optical waveguides. The realization of the method is based on the equivalent straight waveguide approach and consists of two steps. At first, the plane-wave boundary condition is introduced at the computational boundary where the outgoing wave is expected. Then, the optimum location of the computational boundary is determined, corresponding to the maximum of radiation power loss. The optimized computational window helps to significantly reduce the influence of the nonphysical reflections of the outgoing wave caused by the particular index profile of bent waveguide structures in the straight waveguide approach. Using this method,the propagation constants and radiation losses are determined for waveguides with different bend radii. In contrast to methods based on the absorption concept, the proposed method does not require the introduction of additional parameters.
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