Ultra-Compact High-Speed Polarization Division Multiplexing Optical Receiving Chip Enabled by Graphene-on-Plasmonic Slot Waveguide Photodetectors

Polarization multiplexing technology is widely adopted for increasing the capacity in optical communication systems. Especially, silicon-based integrated polarization division multiplexing (PDM) optical receivers with large bandwidth therein play an important role, which are crucial for on-chip large-capacity optical interconnection. Here, a silicon-based PDM optical receiving chip is enabled by two-dimensional grating couplers and graphene-on-plasmonic slot waveguide photodetectors. Utilizing the advantages of the designed focusing two-dimensional grating couplers and plasmonic-slot-waveguide-enhanced graphene-light interaction, the optical receiving chip is achieved with an ultra-small footprint, a bandwidth exceeding 70 GHz and a reception of PDM signals in a line rate of 128 Gbit s(-1) non-return-to-zero and 224 Gbit s(-1) four-level pulse-amplitude-modulation at 1550 nm, accompanied by the bit error rates lower than the KP4 forward error correction threshold and 15% soft-decision forward error correction threshold, respectively. Comparing with receiving the single-polarization state, simultaneous receiving dual-polarization state introduces about 1 dB additional power penalty because of inter-polarization crosstalk. The graphene-plasmonic PDM optical receiving chip can greatly improve the line rate of the system, showing its unique advantages of small footprint, high speed, large bandwidth, low crosstalk and complementary metal-oxide-semiconductor compatibility, which can be potentially used in the next generation silicon-based high-speed optical communication.