Speaker
Description
The outstanding charge transport properties of graphene enable numerous electronic applications of this remarkable material, many of which are expected to operate at ultrahigh, terahertz (THz) rates. In many of these applications, charge carriers in graphene are therefore exposed to very short field transients. Here we show that these THz transients do not only induce charge transport – i.e. linear response –, but also affect the transport in graphene – i.e. nonlinear effects – already for very low field strengths.
We further show that this highly nonlinear response can be used for efficient optical harmonics generation – the multiplication of the photon energy as a result of nonlinear light-matter interaction. We report on the generation of THz harmonics in single-layer graphene under ambient conditions, driven by THz fields on the order of only 10s of kV/cm, and with the field conversion efficiencies as high as $\sim10^{-3}$ and $\sim10^{-4}$ for the third and fifth THz harmonics, respectively. The effective THz nonlinear optical coefficients of graphene χ$^{(3)}$ exceeds that of typical solids by 10 orders of magnitude. The enormousness of the nonlinear optical response can be traced to a fundamentally different origin of the nonlinearity.
