Silicon mode-insensitive modulator for TE0 mode and TE1 mode

Mode-division multiplexing (MDM), which could further increase the capacity and flexibility of the communication systems, has attracted much attention. In this Letter, we demonstrate a proof-of-principle silicon mode-insensitive modulator based on the balanced Mach-Zehnder interferometer that could realize modulation of both TE0 and TE1 modes using a horizontal PN junction. The PN junction is offset from the center of the waveguide to the n-type doped region to modulate both TE0 and TE1 modes effectively. An adiabatic directional coupler is used as a mode-insensitive 3-dB power splitter for both modes. A mode-insensitive thermal phase shifter is used to change the operation point of the modulator. On-off keying modulation at 32 Gb/s is successfully demonstrated for both TE0 and TE1 modes. This modulator can be potentially used in MDM-assisted optical sampling systems.