Ultrabroadband, achromatic, and non-diffracting perfect optical vortex generation via radial momentum control in dielectric metasurfaces

Optical vortices, beams that carry a twist, are pivotal in advanced technologies like optical manipulation, optical communications and imaging. However, their utility has been hampered by a fundamental limitation: the size and spread of the beam change inevitably with its twist and color, making stable, scalable systems difficult to achieve. Here we show that using precisely engineered metasurfaces to control light's radial momentum enables the generation of a class of 'achromatic non-diffracting perfect vortex beams' (ANPVBs). These beams maintain an almost perfectly constant diameter, regardless of their twist or color across the visible spectrum (450-780 nm), and resist spreading over long distances. By decoupling beam size from these previously limiting factors, our work provides a robust and versatile platform for applications in high-capacity optical communication, quantum information processing and imaging.