title: Flat metasurfaces to focus electromagnetic waves in reflection geometry.
abstract: We show that a flat metasurface with a parabolic reflection-phase distribution can focus an impinging plane wave to a point image in reflection geometry. Our system is much thinner than conventional geometric-optics devices and does not suffer the energy-loss issues encountered by many metamaterial devices working in transmission geometry. We designed realistic microwave samples and performed near-field scanning experiments to verify the focusing effect. Experimental results are in good agreement with full wave simulations, model calculations, and theoretical analyses.
authors.affiliation: State Key Laboratory of Surface Physics and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, Shanghai 200433, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Shiyi
authors.initials: S
authors.lastname: Xiao
authors.forename: Bengeng
authors.initials: B
authors.lastname: Cai
authors.forename: Qiong
authors.initials: Q
authors.lastname: He
authors.forename: Tie Jun
authors.initials: TJ
authors.lastname: Cui
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou