Terahertz plasmon resonance absorption in CVD graphene for photodetection applications

We experimentally study the gate-tunable terahertz plasmon resonance in large area grating-coupled CVD graphene. Despite moderate carrier mobility in CVD graphene (~10
³
cm
²
/V/s), the resonance is clearly distinguishable above the Drude absorption background in the 5-10 THz range. The optical scattering time governing the quality factor of plasmon resonance appears to be well above the dc relaxation time. We confirm this relation by simultaneous THz transmission and field-effect measurements. We also show that the presence of the grating coupler in close proximity to graphene modifies the plasmon spectra. The plasmon field becomes tightly bound below the metal stripes, while the frequency depends on the stripe length but not by grating period.