Mode mixing in asymmetric double-trench photonic crystal waveguides

The waveguiding properties of a double-trench waveguide in which a conventional single-mode strip waveguide was embedded in a two-dimensional photonic crystal (PhC) slab formed in silicon-on-insulator wafers were discussed. It was demonstrated that the bandwidth for relatively low-loss waveguiding was significantly expanded to 250 nm. The flat transmission spectrum was found to be interrupted by numerous narrow stop bands. Analysis shows that the stop band were due to anticrossing between TE-like and TM-like modes.