On-chip high-order mode converter and a 10-channel simultaneous polarization- and mode-division-multiplexer

A high-order mode converter and multiplexer based on silicon waveguide is designed. According to the principle of mode coupling, the conversion between high-order modes in different polarization states can be realized, including TM01 to TE11 mode conversion and TE01 to TM11 mode conversion. Using the FDTD method, we analyze in detail the influence of the waveguide width W on the mode refractive index N, as well as the influence of the waveguide width W, the gap G and the coupling length L between different waveguides on the polarization extinction ratio and insertion loss. The results show that the polarization extinction ratio of the designed mode converter is 23.17dB and 24.9dB, the loss is 0.27dB and 0.589dB, and the coupling length is 14 mu m and 9.7 mu m, respectively. Besides, we proposed a 10-channel simultaneous polarization and mode division multiplexing system by the cascade of 10 mode converters, which can further increase the communication capacity.