Lowest-order mode transmission in multimode dielectric S-bends

This paper focuses on the problem of lowest-order mode (LOM) transmission in multimode S-bends given LOM input. Total loss calculations in S-bends using the finite difference beam propagation method (FDBPM) are compared with analytical results. Sine and cosine shaped slab S-bend geometries are studied to determine if mode conversion (to higher-order modes) can be controlled and/or suppressed altogether. Reduction of bending losses for the overall structure is also sought. It is also shown that loss rates for a fixed radius of curvature and total loss in an S-bend are not sensitive to the substrate index. Thus results determined in this paper are applicable to a range of substrate indices. Specifically, it is shown that the results are applicable to ion-exchange glass waveguides.