Second harmonic generation from single nanoparticles

摘要

Nonlinear optics has found applications in many different areas. Although a host of nonlinear phenomena can be studied in individual atoms and molecules, the great majority of the measurements have involved bulk matter. Indeed, the most common description of processes such as second harmonic generation (SHG) relies on the concept of susceptibility, which is a bulk quantity. With the recent progress in nano-optics, however, scientists have begun to explore nonlinear optical processes in subwavelength structures [1–3]. In this case, phase matching becomes unimportant, but issues regarding size and shape of the medium should be considered. In our work, we combine interferometric scattering (iSCAT) [4, 5] with the second harmonic signal recorded from individual noncentrosymmetric inorganic nanocrystals (BaTiO3) and metallic (Au) nanoparticles. By examining each particle also in an electron microscope, we aim to relate the linear and nonlinear optical response of nanoparticles with their shape and size.