Abstract
Two-photon microscopy has become a widespread tool in high-spatial resolution imaging because of the quadratic dependence of absorption on the excitation intensity, which confines fluorescence and photobleaching to the very proximity of the focal volume. Multi-photon photoluminescence (MPPL) processes are also a valuable tool for the characterization of plasmonic noble-metal nanoparticles and nanoantennas since they afford the sensitivity and high spatial resolution which is needed to map field distributions and thus characterize the resonant behavior of the electron plasma oscillations in response to the external optical field. © 2011 IEEE.