Modal analysis of optical rib waveguides with finite lateral cross-section

A novel method based on the effective-index method which reduces the optical rib waveguide having a two-dimensional cross-section into four separate one-dimensional slab waveguides is presented. In order to test the accuracy of proposed method, firstly, dimensions of the rib waveguide are changed so that the two rectangular waveguides with different aspect ratios are obtained and then these structures are analyzed with the proposed method. Secondly, the preceding results are compared with the results of the two rectangular waveguides analyzed by the conventional effective-index method. In consequence of this comparison, it can be seen that there is a good agreement between the results of the proposed method and the effective-index method, especially for square cross-sectioned waveguides