Low-loss and fabrication tolerant silicon mode-order converters based on novel compact tapers.

We propose large bandwidth and high fabrication-tolerance mode-order converters on the silicon-on-insulator platform based on novel compact tapers structures. Each of the converters is in a single waveguide. Designs of different symmetries with and without breaking the parities between odd and even modes are illustrated. The fabrication tolerances of the devices are also investigated. The simulation results show that high conversion efficiencies can be readily achieved over a wavelength range from 1520 nm to 1580 nm for all of the proposed devices. The average conversion efficiencies of TE1-to-TE0, TE2-to-TE0, TE3-to-TE0, TE2-to-TE1, TE3-to-TE1, and TE3-to-TE2 converters are -0.061 dB, -0.052 dB, -0.11 dB, -0.119 dB, -0.168 dB, and -0.154 dB, respectively. The conversion efficiencies have negligible degradations under normal width and thickness deviations.