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Pure α-La(IO 3 ) 3 and α-La 0.85 Er 0.15 (IO 3 ) 3 nanocrystals were synthesized by a microwave-assisted hydrothermal method leading to a reaction yield of 87 ± 4%. Electron microscopy and dynamic light scattering characterizations provide evidence for the formation of nanocrystals with an average size of 45 ± 10 nm for α-La(IO 3 ) 3 and 55 ± 10 nm for α-La 0.85 Er 0.15 (IO 3 ) 3 . When dispersed in ethylene glycol, the nanocrystal suspensions exhibit second-harmonic generation under near-infrared excitations at 800 and 980 nm whereas additional photoluminescence by up-conversion is simultaneously observed in the case of α-La 0.85 Er 0.15 (IO 3 ) 3 nanocrystals. Quantitative assessments of the second-harmonic generation efficiency from second-harmonic scattering experiments at 1064 nm result in relatively high ⟨d⟩ coefficients measured at 8.2 ± 2.0 and 8.0 ± 2.0 pm V −1 for α-La(IO 3 ) 3 and α-La 0.85 Er 0.15 (IO 3 ) 3 , respectively. The relative intensity between second-harmonic generation and photoluminescence is discussed following the excitation wavelength.

We use Hyper Rayleigh Scattering and polarization resolved multiphoton microscopy to investigate simultaneously the second and third-order nonlinear response of Potassium Niobate and Bismuth Ferrite harmonic nanoparticles. We first derive the second-to-third harmonic intensity ratio for colloidal ensembles and estimate the average third-order efficiency of these two materials. Successively, we explore the orientation dependent tensorial response of individual nanoparticles fixed on a substrate. The multi-order polarization resolved emission curves are globally fitted with an analytical model to retrieve individual elements of susceptibility tensors.

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Dispersion of the absolute second-order susceptibility of both MoS 2 and WS 2 is assessed on a wide spectral excitation range (710-1300 nm) by using second-harmonic scattering spectroscopy (SHS). SHS is an accurate ensemble measurement here applied on well-dispersed suspensions of monodisperse liquid-exfoliated nanosheets showing a high monolayer content. The as-derived, high susceptibility values shed light on the discrepancies between available literature values while evidencing resonances associated with the main excitonic transitions.