Highly efficient avalanche multiphoton luminescence from coupled Au nanowires in the visible region

We demonstrate highly efficient avalanche multiphoton luminescence (MPL) from ordered-arrayed gold nanowires (NWs) with low time-average excitation intensity, I-exc (5.0-9.1 kW/cm(2)). The intensity of avalanche MPL, I-MPL, is about 10(4) times larger than that of three-photon luminescence, the slope partial derivative log I-MPL/partial derivative log I-exc of avalanche MPL reaches as high as 18.3, and the corresponding polarization dependence of I-MPL has a form of cos(50) phi(p). The emission dynamics of avalanche MPL and three-photon luminescence are also studied comparatively. These observations indicate that the highly efficient avalanche MPL is attributed to the giant enhancement and coupling of longitudinal surface plasmon resonance of ordered-arrayed gold NWs.