Properties of Photoluminescence from Single Gold Nanorods Induced by Near-Field Two-Photon Excitation

We investigated properties of photoluminescence from single gold nanorods induced by near-field two-photon excitation, using scanning near-field optical microscopy. Photoluminescence spectrum showed two peaks around 550 and 650 nm in wavelengths regardless of the rod dimensions, whereas the intensity ratio of the two spectral components varies from rod to rod. We discussed the observed spectral features of photoluminescence based on electromagnetic calculations and found that the observed spectral features can be explained in terms of local field enhancement in the vicinity of the gold nanorod due to plasmon-mode excitation.