Multiwavelength achromatic super-resolution focusing via a metasurface-empowered controlled generation of focused cylindrically polarized vortex beams.

Abstract

Non-invasive imaging beyond the diffraction limit and free from fluorescent labels in the visible is highly desired for microscopy. It remains a challenge to obtain such super-resolution focusing along with multiwavelength achromatic performance in the far field using an integratable and easily designed system. In this work, we demonstrate a straightforward metasurface-based method to realize multiwavelength achromatic generation and focusing of cylindrically polarized vortex beams (CPVBs). Attributed to the extra degrees of freedom of CPVBs and multi-section design, we have realized multiwavelength achromatic super-resolution focusing in the air with focal size tighter than that of normally used schemes like immersion metalenses or focused radially polarized beams. It is expected that this metasurface-empowered ultra-compact design will benefit potential applications which call for high resolution, like optical microscopy, laser processing, etc.