Microwave Synthesis and Up-Conversion Properties of SHG-Active α-(La, Er)(IO3)3 Nanocrystals.

Pure α-La(IO3)3 and α-La0.85Er0.15(IO3)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(IO3)3 and 55 ± 10 nm for α-La0.85Er0.15(IO3)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-La0.85Er0.15(IO3)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(IO3)3 and α-La0.85Er0.15(IO3)3, respectively. The relative intensity between second-harmonic generation and photoluminescence is discussed following the excitation wavelength.

Nonlinear optical susceptibility of two-dimensional WS2 measured by hyper Rayleigh scattering: erratum.

This erratum corrects errors in the expressions for ⟨ßTMD⟩ and fitted form of IHRS and a consequent data point in Fig. 4 of a recent Letter [Opt. Lett.42, 5018 (2017)OPLEDP0146-959210.1364/OL.42.005018]. It also supplies data for the reference compound para-nitroaniline (pNA). The correction to ⟨ßTMD⟩ improves experimental agreement from 46% to within 21% of independent scissors-corrected density functional theory (DFT) calculations. Central findings from the original Letter remain intact.

Bismuth ferrite dielectric nanoparticles excited at telecom wavelengths as multicolor sources by second, third, and fourth harmonic generation.

We demonstrate the simultaneous generation of second, third, and fourth harmonics from a single dielectric bismuth ferrite nanoparticle excited using a telecom fiber laser at 1560 nm. We first characterize the signals associated with different nonlinear orders in terms of spectrum, excitation intensity dependence, and relative signal strengths. Successively, on the basis of the polarization-resolved emission curves of the three harmonics, we discuss the interplay of susceptibility tensor components at different orders and show how polarization can be used as an optical handle to control the relative frequency conversion properties.

Nonlinear optical susceptibility of two-dimensional WS2 measured by hyper Rayleigh scattering.

Hyper Rayleigh scattering (HRS) was used to measure the second-order nonlinear susceptibility, χ(2), for liquid exfoliated WS2 monolayers. To the best of our knowledge, it is the first reported application of the HRS technique to assess the bulk-like χ(2) of a two-dimensional (2D) material. The concentration-dependent HRS signal indicated a 4.90±0.30×10-25 esu first hyperpolarizability for 42 nm WS2 monolayers under 1064 nm laser irradiation using para-nitroaniline as an external reference. The corresponding value of χxxx(2) was calculated to be 460±28 pm V-1. This was within 46% of independent density functional theory predictions. Agreement with theory was improved over related microscopy-based approaches. These results support the use of HRS to evaluate 2D materials for nonlinear frequency mixing applications.

Multi-Order Investigation of the Nonlinear Susceptibility Tensors of Individual Nanoparticles.

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.