Three-dimensional orientation-unlimited polarization encryption by a single optically configured vectorial beam

The interplay between light polarization and matter is the basis of many fundamental physical processes and applications. However, the electromagnetic wave nature of light in free space sets a fundamental limit on the three-dimensional polarization orientation of a light beam. Although a high numerical aperture objective can be used to bend the wavefront of a radially polarized beam to generate the longitudinal polarization state in the focal volume, the arbitrary three-dimensional polarization orientation of a beam has not been achieved yet. Here we present a novel technique for generating arbitrary three-dimensional polarization orientation by a single optically configured vectorial beam. As a consequence, by applying this technique to gold nanorods, orientation-unlimited polarization encryption with ultra-security is demonstrated. These results represent a new landmark of the orientation-unlimited three-dimensional polarization control of the light–matter interaction. Generating arbitrary orientation of light polarization has been an elusive goal, yet it is important to light interactions with nano-objects. By combining azimuthally and radially polarized beams, Liet al. overcome this obstacle and demonstrate its use for polarization-based encryption with gold nanorods.