Analysis of higher-order mode suppressed transmission in low-loss silicon multimode waveguides on silicon-on-insulator substrates.

Higher-order mode coupling at bending waveguides between Si multimode waveguides and 500-nm-wide wire waveguides was evaluated for low-loss Si multimode waveguide circuits. By narrowing the multimode waveguides to the wire waveguides at the bending section, the TE fundamental mode propagation was strongly maintained in the entire circuit, and the spectral fluctuation was improved from 10 dB to less than 1 dB for a 4-µm-wide waveguide. Furthermore, propagation losses were reduced to less than 1 dB/cm with waveguide widths greater than 1 µm. [ABSTRACT FROM AUTHOR]