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Regular arrays of rectangular gold nanoparticles placed on gold films are characterized by using linear
reflection spectroscopy (in the wavelength range of 450-950 nm) and nonlinear scanning optical microscopy,
in which two-photon photoluminescence (TPL) excited with a strongly focused laser beam (in the wavelength
range of 730-820 nm) is detected. Experimental results are modeled using a finite-difference time-domain
approach with the dielectric function of gold approximated by a Drude-Lorentz formula, showing a rather good
agreement between the experimental and theoretical reflection and TPL enhancement spectra. The modeling is
also used to optimize the array parameters for achieving strong and well-pronounced TPL enhancement
maxima in the wavelength range accessible to the used experimental techniques, i.e., close to 800 nm. Accordingly
designed samples are fabricated and characterized, corroborating the modeling predictions. The origin of TPL enhancement
and its relation to local-field enhancements at the sample surface as well as its
characterization with TPL microscopy is discussed here. The implications of the obtained results are also discussed.
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