COMPARATIVE-ANALYSIS OF THE METHOD-OF-LINES FOR 3-DIMENSIONAL CURVED DIELECTRIC WAVE-GUIDES

We discuss the effects of waveguide geometry on the radiation loss of tightly curved multimode dielectric waveguides. Three waveguide geomet ries are investigated: a ridge waveguide, a buried waveguide, and an i nterdiffused waveguide, We compare the effective index method with bot h semi- and full-vectorial method-of-lines analyses for these waveguid e geometries. This comparison shows that the effective index method is accurate for curved waveguides except where the outer confinement reg ion is in cut-off or, in the case of TM-polarization, for the ridge wa veguide, In the latter case, the full-vectorial method-of-lines predic ts a resonant feature of the TM-mode radiation loss of curved ridge wa veguides; this is not predicted by either the semivectorial method-of- lines or the effective index method.