Hot-electron emission processes in waveguide-integrated graphene

Photoemission plays a central role in a wide range of fields, from electronic structure measurements to free-electron laser sources. In metallic emitters, single-photon1, multiphoton2–5 or strong-field emission6–10 processes are the primary photoemission mechanisms. Here, using a sub-work-function 3.06 eV continuous-wave laser, photoemission from waveguide-integrated monolayer graphene is observed to occur at peak power densities >5 orders of magnitude lower than reported multiphoton and strong-field emission6,11,12. The behaviour is explained by the emission of hot electrons in graphene. In monolayer graphene, the need for photoelectrons to be transported to an emitting surface is eliminated, dramatically enhancing the probability of emission before thermalization. These results indicate that integrated-photonics-driven hot-electron emission provides a rich new area of exploration for both electron emission and integrated photonics.