  We report an optoelectronic mixer based on chemical vapour-deposited
graphene. Our device consists in a coplanar waveguide that integrates a
graphene channel, passivated with an atomic layer-deposited Al2O3 film. With
this new structure, 30 GHz optoelectronic mixing in commercially-available
graphene is demonstrated for the first time. In particular, using a 30 GHz
intensity-modulated optical signal and a 29.9 GHz electrical signal, we show
frequency downconversion to 100 MHz. These results open promising perspectives
in the domain of optoelectronics for radar and radio-communication systems.
