Gate-tunable optical extinction of graphene nanoribbon nanoclusters

We investigate the optical response of graphene nanoribbons (GNRs) using the broadband nonlinear generation and detection capabilities of nanoscale junctions created at the LaAlO3/SrTiO3 interface. GNR nanoclusters measured to be as small as 1–2 GNRs in size are deposited on the LaAlO3 surface with an atomic force microscope tip. Time-resolved nonlinear optical probes of GNR nanoclusters reveal a strong, gate-tunable second and third harmonic response, as well as strong extinction of visible to near-infrared light at distinct wavelengths, similar to previous reports with graphene