Incoherent second-harmonic generation by NaNbO3 nanocrystals with sizes from ≈ 60 nm to ≈ 100 nm

Abstract

The second-order nonlinearity of sodium niobate (NaNbO₃) nanocrystals (NCs) was investigated as a function of their size. NCs with average dimensions from $\approx$ 60 nm to $\approx$ 100 nm were synthesized by the Pechini's method, and the studies were carried out by using the hyper-Rayleigh scattering technique to investigate the efficiency of incoherent second harmonic generation. A Nd:YAG laser (1064 nm, 7 ns, 10 Hz) was the excitation source which generated emission centered at 532 nm. The measured nonlinear (NL) optical coefficient, $d$, proportional to the first order hyperpolarizability, increases with decreasing the average particle size, ranging from 3.2 p.m./V to 4.7 pm/V. The results corroborate the previous reports that indicated NaNbO₃ NCs as highly promising for bioimaging microscopy and confirm their large potential for devices based on NL optical phenomena.