Analysis of Mode Hybridization in Tapered Waveguides

The mode hybridization of tapered submicron silicon optical waveguides is analyzed by eigenmode expansion. We study the mode conversion effects related to the waveguide vertical symmetries and taper lengths. A curving design for TM-TE high-order mode conversion in single effective index line is presented by us, which is shorter than the reported linear taper design. Besides, we propose a new type of mode conversion between TM and TE high-order mode, which is called the crossband conversion. The novel design has wide bandwidth and good fabrication tolerance. These concepts can be useful for high-order modes control issues, such as TM mode guiding from very wide to narrow waveguide core.