Nanoscale control over optical singularities

Optical singularities have attracted much interest in the past decades, enabling advancements in nano-manipulation, bio-sensing, and quantum optics, owing to their ability to carry and transfer angular momentum on the nano scale. Optical vortices (OVs), in this respect, are phase singularities useful for many applications, such as particle trapping and manipulation, optical communication, and super-resolution. Vectorial OVs also exhibit polarization singularities, known as C-points, which have been used in recent years to control emission from quantum emitters. Here, we present continuous nanoscale spatial control over optical singularities on a metal-air interface by varying the polarization state of the light exciting surface plasmon polaritons through a spiral slit. We demonstrate our method using phase-resolved near-field microscopy. Such control over optical singularities opens up exciting possibilities for light in two dimensions, ranging from new light-matter interactions on a chip to efficiently controlled nanomotors.