title: Ultrafast photoluminescence from graphene.
abstract: Since graphene has no band gap, photoluminescence is not expected from relaxed charge carriers. We have, however, observed significant light emission from graphene under excitation by ultrashort (30-fs) laser pulses. Light emission was found to occur across the visible spectral range (1.7-3.5 eV), with emitted photon energies exceeding that of the excitation laser (1.5 eV). The emission exhibits a nonlinear dependence on the laser fluence. In two-pulse correlation measurements, a dominant relaxation time of tens of femtoseconds is observed. A two-temperature model describing the electrons and their interaction with strongly coupled optical phonons can account for the experimental observations.
authors.affiliation: Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA.
authors.forename: Chun Hung
authors.initials: CH
authors.lastname: Lui
authors.forename: Kin Fai
authors.initials: KF
authors.lastname: Mak
authors.forename: Jie
authors.initials: J
authors.lastname: Shan
authors.forename: Tony F
authors.initials: TF
authors.lastname: Heinz