Nonlinear frequency conversion and manipulation of vector beams.

Vector beams have been extensively investigated in recent years because of their fascinating vector character across the beam transverse section, which is demonstrated to be useful for optical micro-manipulation, optical micro-fabrication, optical communication, single molecule imaging, and so on. To date, it is still a challenge to realize nonlinear frequency conversion and manipulation of such vector beams because of the polarization sensitivity in most nonlinear processes. Here, for the first time, to the best of our knowledge, we generate second-harmonic vector beams by using three-wave mixing processes in our experiment, which occur in two orthogonally placed nonlinear crystals, and the vector property is recognized by using a Glan-Taylor polarizer. This nonlinear frequency conversion process enables vector beams to be obtained at new wavelengths, and opens up new possibilities for all-optical switching and manipulation of vector beams.