Two-photon imaging of field enhancement by groups of gold nanostrip antennas

Resonant field enhancement by groups of 16 nm thin gold nanostrip antennas consisting of four strips (widths of 70, 100, and 130 nm) and fixed gap (50, 100, 150, or 200 nm) between them and positioned on a quartz substrate is investigated by reflection spectroscopy and two-photon photoluminescence scanning optical microscopy. We obtain good agreement with theoretical calculated reflection spectra and the investigated two-photon intensity dependence on the nanoantenna configurations and parameters of the illumination showed field enhancements increasing with increasing gaps in each group for the p-polarized (resonant) excitation, whereas these enhancement effects were not observed for the s-polarization (nonresonant) excitation. (C) 2009 Optical Society of America