Ultra-Compact Multimode Waveguide Bends Based on the Inverse Design

A method of designing silicon multimode waveguide bends using inverse design algorithm is presented in this paper. High-performance and ultra-compact multimode waveguide bending structures are realized by using a special curve consisting of multiple arcs with different radii of curvature. The bent waveguide supporting three modes with an effective bending radius of only 9.35um is designed and tested. The theoretical excess losses of TE0, TE1 and TE2 modes are less than 0.04 dB in a wide spectral range from 1500 to 1600 nm, and the crosstalk's between all guided modes are all lower than -26 dB. Besides the fabrication of the present structure is simple without additional etching step.