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 of the time-domain response, 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.
@article{arxiv.1006.5769,
title = {Ultrafast Photoluminescence from Graphene},
author = {Chun Hung Lui and Kin Fai Mak and Jie Shan and Tony F. Heinz},
journal= {arXiv preprint arXiv:1006.5769},
year = {2010}
}
Comments
13 pages, 7 figures, supplemental material included