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Femtosecond Laser-Excited Two-Photon Fluorescence Microscopy of Surface Plasmon Polariton

We demonstrate microscopic imaging of surface plasmon polaritons (SPPs) on silver films excited by 11 fs near-infrared laser pulses. A fluorescence layer placed on the silver film converts surface electromagnetic fields to propagating lights in visible wavelengths via two-photon excitation process. The wavelength of SPP determined from fluorescence micrographs agrees well with the calculated value of SPP at the silver-fluorescent film interface.