Anomalous deflection based on three-dimensional variable nanopillar metasurfaces

A metal-dielectric-metal nanopillar metasurfaces with variable three-dimensional sizes is proposed and experimentally demonstrated to achieve anomalous deflection at different angles with different phase gradients. Theoretical studies have shown that subwavelength nanopillar with different lengths, widths and heights on a glass substrate can achieve high amplitude response and complete 2π phase delay in the reflection field. Anomalous deflection metasurfaces with three phase gradients of π/2, π/4 or π/8 in supercell units composed of 4, 8, or 16 nanopillars of different sizes working at wavelength of 1550 nm are designed and investigated. Under linearly polarized normal incident beam, the anomalous deflection angles of the three phase gradients are, respectively, 23.97°, 12.21° and 5.87° with a reflection of 83%, which is consistent with the generalized Snell's theory. The negative refraction and total reflection phenomenon under the oblique incident beams are generated in the case of phase gradient of π/4, which are completely consistent with the numerical results. Using two-photon laser direct writing technology, a metasurface with π/2 phase gradient nanopillar was fabricated on a 170 μm thick borosilicate glass substrate. The anomalous deflection angle measured by infrared polarization detection is 24°, which is essentially the same as the designed value. The demonstrated work provides a new way for realizing artificial control of electromagnetic wave propagation in optical communication and other fields.