  We have theoretically studied a graphene-based plasmonic waveguide, which can
gate the transmission of a surface plasmon polariton (SPP) localized at the
graphene-semiconductor interface. When a gate voltage is applied above a
certain critical value, the charge density modulation in the quasi
two-dimensional electron gas formed in the inversion layer can induce a local
plasma resonance. Since the local plasma resonance is strongly coupled to the
SPP, it can suppress the transmission of the SPP. By calculating the
propagation length of the SPP with varying gate voltage, we have obtained the
sharp switching line shape. We have demonstrated that the wavelength of the SPP
can be reduced below ~1/100 of that of an incident light and the propagation
length of the SPP can be significantly reduced by a factor of ~15 upon
switching. This ensures that our plasmonic waveguide can operate effectively as
a plasmonic switch for the SPP.
