Terahertz plasmons in grating-coupled large-area graphene transistors

We demonstrate the excitation of gate-tunable terahertz plasmon resonance in large area grating-coupled CVD graphene using Fourier spectroscopy. We find that the resonance is clearly distinguishable above the Drude absorption background in the 5-10 THz range despite moderate carrier mobility in CVD graphene (∼103 cm2/V/s). Besides, plasmon lifetime in CVD graphene samples exceeds the transport relaxation from dc mobility measurements. We confirm this ratio by simultaneous THz transmission spectroscopy and field-effect measurements. We also show the plasmon spectra modification related to the presence of the grating coupler in close proximity to graphene. The plasmon field becomes tightly bound below the metal stripes, while the frequency depends on the stripe length but not by grating period.