Morphology and polarization-dependent second harmonic generation in single hexagonal sodium niobate micro/nano-crystals

We synthesized NaNbO3 micro/nano-crystals with six morphologies and three different crystal structures using the hydrothermal method. Each single hexagonal NaNbO3 micro/nano-crystal (samples No. 1–3) exhibited a strong second-order nonlinear response. By calculating the average intensity and measuring the polarization response of each of these hexagonal crystals (samples No. 1–3), it was demonstrated that the same crystal structure displays a similar optical second harmonic generation (SHG) response. Furthermore, SHG was shown to be independent of the morphology and identical for similar crystals, which is expected for a volume effect with a second-order susceptibility tensor depending on the properties of the material. The optical SHG properties of these NaNbO3 micro/nano-crystals together with the previous related research suggest that these non-toxic crystals may find promising applications in biological imaging and related fields.