Opportunities for Wideband Wavelength Conversion in Foundry Compatible Silicon Waveguides Covered With Graphene
We numerically examine the opportunities for wideband wavelength conversion through four wave mixing (FWM) in a foundry compatible 220 nm thick silicon on insulator (SOI) waveguide covered with the highly nonlinear two dimensional material of graphene. As a case study, we consider a foundry compatible SOI waveguide shaped as a double spiral and covered with two separate graphene sheets, which are covered in turn by two solid polymer electrolyte gates. When combining subwatt level pump powers with a short waveguide length of only a few hundreds of micrometers, "perfectly phase matched" conversion with significant efficiencies close to 20 dB can be obtained over a more than 40 THz wide signal band adjacent to the pump frequency. Because of the tunability of the graphene properties using the electrolyte top gates, it is also possible to obtain "quasi phase matched" FWM conversion through a periodic sign reversal of the graphene third order nonlinearity along the waveguide. Conversion efficiencies exceeding 30 dB can be achieved over a 3.4 THz wide signal band that is situated as much as 58 THz away from the pump frequency. Finally, the tunability of the graphene also allows for switching the converter from the perfectly phase matched to the quasi phase matched operation mode.
IEEE Journal of Selected Topics in Quantum Electronics