Graphene, a well-known two-dimensional sheet of carbon atoms in a honeycomb structure, has many unique and
fascinating properties in optoelectronics and photonics. Integration of graphene on silicon nanophotonic wires is a
promising approach to enhance light-graphene interactions. In this paper, we demonstrate on-chip silicon nanophotonic
wires covered by graphene with CMOS-compatible fabrication processes. Under the illumination of pump light on the
graphene sheet, a loss reduction of silicon nanophotonic wires, which is called optically induced transparency (OIT)
effect, is observed over a broad wavelength range for the first time. The pump power required to generate the OIT effect
is as low as ~0.1mW and the corresponding power density is about 2×103mW/cm2, which is significantly different from the saturated absorption effect of graphene reported previously. The extremely low power density implies a new mechanism for the present OIT effect, which will be beneficial to realize silicon on-chip all-optical controlling in the future. It also suggests a new and efficient approach to tune the carrier concentration (doping level) in graphene optically.
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