Two-photon luminescence microscopy of field enhancement at gold nanoparticles

Using a reflection scanning optical microscope detecting two-photon luminescence (TPL) we have imaged square gold bumps positioned in a periodic array either on a smooth gold film or directly on a glass substrate. The second-harmonic (SH) and TPL response from these structures show both polarization and wavelength dependence. The gold bumps on gold film showed extremely high sensitivity to the incident field, with the strongest TPL response from the gold bumps being enhanced nearly 10(3) times compared to the TPL response from the smooth gold surface. For gold bumps directly on glass the similar calculated enhancement was estimated to be similar to 10(2). (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.