Design on plasma metalenses based on Pancharatnam–Berry phase

Abstract Conventional lenses utilize phase accumulation to modulate light waves. Due to the continuity of the lens surface, the thickness of these lenses is much greater than the wavelength of incident light, resulting in bulky volumes and small numerical apertures (NAs). Fresnel lenses, on the other hand, suffer from loss of imaging details. With current technological advancements, there is an urgent need for optical lenses with higher precision and smaller sizes. This paper conducts an in-depth investigation into the focusing method of metalenses modulated by the geometric phase (Pancharatnam–Berry phase) of metasurfaces. By designing rectangular nano-block unit structures and leveraging their rotation angles to modulate the phase of incident light, efficient focusing in the visible band ( λ = 861 nm) is achieved. Additionally, the fabrication complexity is significantly reduced by etching vanadium dioxide (VO₂) rectangular blocks on a polyimide substrate. Simulation results demonstrate that the designed metalens achieves a NA of 0.78 and a full width at half maximum of 570 nm, approaching the diffraction limit. This research holds significant importance for the development of zoomable metalenses in the terahertz band.