In this paper, we numerically investigate the lateral leakage loss behavior for TM-like modes in silicon-on-insulator ridge waveguides. If the waveguide width is set to satisfy a certain condition, the leakage loss of the TM-like mode leads to be a minimum. When utilizing TM-like modes in the ridge waveguides, it is the main drawback that the tolerance for the variations in the waveguide width and operation wavelength is too small. In this paper, we propose a novel ridge waveguide structure, where a dimple is introduced at the ridge region. It is shown from the finite-element analysis that the ridge waveguide with a dimple is both low loss and fabrication tolerant.
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