GaAs gradient metasurface for vortex beam emission with high deflection angles

This study experimentally demonstrates metasurfaces capable of producing output emissions with deflection angles greater than 75 degrees. These metasurfaces are composed of high-aspect-ratio gallium arsenide (GaAs) nano-resonators on double-sided polished GaAs substrates, operating reflectively at a wavelength of 650 nm. Beyond deflecting the incident light beam, the metasurfaces are successfully shown to generate high-deflection-angle, doughnut-shaped emissions by incorporating vortex beam (VB) structured light with a topological charge of up to 8. The broadband capabilities of these metasurfaces are also explored in this work. This work significantly advances the manipulation of structured light. Achieving high deflection angles opens new pathways for developing compact optical systems that leverage the unique properties of vortex beams in a range of applications.