Ultra-Sharp Multimode Waveguide Bends With Dual Polarizations

A silicon-based on-chip ultra-sharp multimode wave-guide bend (MWB) is proposed to work for dual polarizations by introducing modified Euler-curves and shallowly-etched non-uniform subwavelength-gratings (SWGs). For the designed 90 degrees MWB with a core width of 1.01 mu m and an effective bending radius as small as 10 mu m, the excess losses are less than 0.23 dB and the inter-mode crosstalk is lower than <-26.5 dB over a broad band from 1500 nm to 1600 nm for six mode-channels, including three TE-polarization modes and three TM-polarization modes. It shows a great improvement compared to a regular 90 degrees arc-bend.