First measurement of multi-harmonics generation from a single nanoparticle

Tensorial properties of two different nonlinear orders simultaneously accessed and modelled

The authors 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.

The great richness and potential for new applications of nonlinear optics resides in the multiple different signals that can be generated simultaneously. For example, second order susceptibility response, χ(2), already accounts for second harmonic generation, frequency mixing, and optical rectification. Increasing nonlinear order corresponds to a further increase in the number of different signals that can be accessed and prospectively exploited for sensing or imaging. However, the simultaneous collection of emissions stemming from different χ(n) orders from a single object has been scarcely reported to date, due to several complications associated with this measurement. In this work the authors performed an investigation of the simultaneous harmonic emission by two different nanomaterials, KN and BFO. To our best knowledge, this represents the first work were the tensorial properties of two different nonlinear orders are simultaneously accessed and modelled. The ensemble measurements by HRS indicate an intensity ratio among the two nonlinear orders of respectively 30 and 322 under 11 GW/cm2 intensity at 1064 nm which allowed us to estimate the orientationally averaged third order nonlinear efficiencies for these two nanomaterials (χ BFO(3) = 5.5 × 10−18 m2/V2 vs  = 1 × 10-19 χKN(3) 19 m2/V2). For KN the retrieved value is in line with previous works. The smaller value for the SH/TH ratio observed for BFO, together with its much higher absolute intensity for SH (160 pm/V vs 16.6 pm/V) is indeed very favourable for setting-up multi-harmonic detection protocols, which have been demonstrated with the aim of increasing HNP detection selectivity against endogenous signal hindrance. Reference: Schmidt, C., J. Riporto, A. Uldry, A. Rogov, Y. Mugnier, R. L. Dantec, J.-P. Wolf and L. Bonacina (2016). Multi-Order Investigation of the Nonlinear Susceptibility Tensors of Individual Nanoparticles. Sci. Rep. 6: 25415. (10.1038/srep25415) Schmidt-2016 (707 KB).