Novel tunable graphene-based metasurface of metalens

We propose a graphene-based metasurface of metalens, which consists of a ring structure composed of double oblique slits and four semicircular grooves. As the thickness of the base layer increases with the radius, the propagation length shows a decreasing trend and the effective refractive index is the opposite. Under the action of the incident wave at 632.8 nm, the surface plasmon polaritons (SPPs) generated in the double oblique slits interfere with the semicircular grooves at different positions to form different phase delays. SPPs propagate to a distant focus, and appear the focusing phenomenon in space, with the focal length and full height at half maximum reaching 2.7 mu m and 284 nm, respectively. At the same time, the focusing intensity can be flexibly adjusted by changing the graphene Fermi level. Finally, the designed metalens was used for lithography research, and the contrast ratio was 0.98. The research of this metalens has been widely used in energy harvesting, imaging and sensing.