Nanophotonic modulator based on Silicon-ITO heterojunction and slot waveguide with 2D-graphene sheet

A nanophotonic modulator is proposed based on Silicon-ITO (Indium Tin Oxide) heterojunction and slot waveguide with 2D-graphene sheets. It combines the advantage of 2D materials, heterojunctions, and slot waveguides. A 1550-nm light is guided and confined in a nano slot of p-silicon rib, which is filled with semimetal n-ITO. The graphene sheet is used for modulation due to its unique properties, such as absorption turned off due to state filling or Pauli-blocking, to minimize the insertion loss to 0.07 dB/µm with the tuning of Fermi levels in an extensive range of wavelengths at different voltages. The device has shown dual characteristics at different sets of voltages. It works as an absorptive modulator (amplitude modulator) between 0 and 2 V and as an electro-optic modulator from 2 to 5 V. An outstanding π shift at only 32 µm for a voltage of 3 V and a very high extinction ratio of 25 dB for 20 µm of the waveguide is observed. The electrical characteristic of the device shows low power consumption active device length product of VπL = 64 Vµm. A study of TE polarization of light using graphene sheets is also presented in this paper. The device has applications for phase and amplitude modulations in silicon on-chip communication and interconnects.