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Silver nanoplates have obvious advantages compared with other silver structural nanoparticles due to their wide tunability of the local surface plasmon resonance (LSPR) and significant local field enhancement around the sharp corners. Nonlinear optical absorption (NLA) and nonlinear optical refraction (NLR) are widely employed to characterize the nonlinear optical properties due to their simply testing requirement and comparable valuable results. Z-scan method is widely used in optical characterization of nonlinear properties of different materials. Here, a seed-mediated growth method of the silver nanoplates with well controlled size and local surface plasmon wavelength is presented. The nanoparticle size increases gradually and becomes more uniform distribution as the red-shift of the plasmon resonance wavelength from 650 nm to 950 nm. In particular, we show the dependence of NLA and NLR of the silver nanoplates on the LSPR. The absolute value of effective NLA coefficient increases from 1.38 to 4 cm/GW and that of the NLR index increases as large as 3 times when the LSPR wavelength changes from 728 nm to 898 nm, which is attributed to the strong plasmon absorption and local filed enhancement of larger size silver nanoplates. These findings have great potentials in the explorations of functional non-linear devices.

To investigate the influence of surface trapping and dark states on CdSe and CdSe/ZnS quantum dots (QDs), we studied the absorption, fluorescence intensity and lifetime by using one-and two-photon excitation, respectively. Experimental results show that both one- and two-photon fluorescence emission efficiencies of the QDs enhance greatly and the lifetime increase after capping CdSe with ZnS due to the effective surface passivation. The lifetime of one-photon fluorescence of CdSe and CdSe/ZnS QDs increase with increasing emission wavelength in a supralinear way, which is attributed to the energy transfer of dark excitons. On the contrary, the lifetime of two-photon fluorescence of bare and core-shell QDs decrease with increasing emission wavelength, and this indicates that the surface trapping is the dominant decay mechanism in this case.

The relative probability of two- and three-photon absorption in Au nanoparticles was adjusted by tuning the surface-plasmon-resonance (SPR) wavelength and the excitation intensity. Consequently, highly efficient three-photon luminescence from Au nanoparticles with strong SPR enhancement was observed. The decay rate and polarization of two- and three-photon luminescence from Au nanoparticles were comparatively studied. Furthermore, the multiphoton luminescence from Au nanoparticles was used to investigate the resonant energy transfer from CdSe semiconductor quantum dots.

The nanosized (Au,Ag)–Ti three-component granular composite films on glass substrates were prepared using an rf co-sputtering method, and the deposited films were annealed in air. The optical absorption and the ultrafast third-order nonlinearity of the (Au,Ag)–TiO2 films annealed at different temperatures were investigated. The composite film annealed at 600°C exhibits strong resonant absorption at wavelengths of 400 and 670 nm. The ultrafast third-order nonlinear optical susceptibility at 820 nm of the phase separated (Au,Ag)–TiO2 composite film is measured to be 7.4 × 10−9 esu. This is about 70% larger than that of the Au–TiO2 composite film.

The porous nanosized poly-crystal LiNbO3 film on the fused SiO2 substrate was prepared by using r.f. sputtering method. The microstructure and the third-order optical nonlinearity of the film were investigated. The size of the micro-crystal grains was in the range of 110–160 nm, and the average pore size was 80 nm. The magnitude of ultrafast response χ (3) of the sputtered thin LiNbO3 film at 830 nm wavelength was estimated to be as large as 1.9 × 10 −8 esu, which is 4 orders of magnitude larger than that of LiNbO3 single crystal.

We demonstrate highly efficient avalanche multiphoton luminescence (MPL) from ordered-arrayed gold nanowires (NWs) with low time-average excitation intensity, Iexc (5.0-9.1 kW/cm2). The intensity of avalanche MPL, IMPL, is about 10(4) times larger than that of three-photon luminescence, the slope partial differential log IMPL/ partial differential log Iexc of avalanche MPL reaches as high as 18.3, and the corresponding polarization dependence of IMPL has a form of cos50 phip. 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.

We report the spatial intensity distributions of the laser-induced charge and spin polarizations in GaAs∕AlGaAs two-dimensional electron gas (2DEG) detected by using second harmonic generation (SHG) imaging technique. The spin polarized electrons in the 2DEG are pumped by a single linear polarized laser beam and probed by another beam which produces reflective SHG. By comparing the images of SHG probed with left- and right-circular polarized laser beams, the spatial distributions of the effective charge and spin polarizations in the 2DEG sample are mapped out.