Investigation of KTiOPO4 nanocrystals by means of second-harmonic light emission

The finding of nonlinear nanometric-sized probes is of key importance for the development of nonlinear microscopy in physical as well as biological sciences. We isolate nonlinear KTiOPO₄ nanocrystals and study them by second-harmonic generation microscopy and atomic force microscopy independently. With both polarization analysis and defocused imaging of the emitted second harmonic field, we extract the Euler angles of the crystalline axes of a single nanocrystal. The nonlinear features of a single KTiOPO ₄ nanocrystal makes it a good candidate for a vectorial probe of electromagnetic near-fields and coherent imaging.