Fig. 1. (a) Schematic of the basic MCSA unit cell consisting of a slot antenna on top of an SiO2 spacer and an Au mirror. (b) Numerically calculated complex reflection coefficients as a function of the slot antenna lateral dimensions at the design wavelength of λ=785nm upon TM polarization. The SiO2 spacer thickness is set to ts=130nm. The amplitude |rxx| is visualized by the color map, while the dashed blue lines are the contours of the reflection phase φxx ascending by a 20-deg phase step. (c) Cross-sectional electric field distributions in different cutting planes for the slot antenna with Lx=40nm and Ly=150nm at λ=785nm. The selected cutting planes display the mode profiles within the center of the slot antenna in the top Au layer. The color bars are chosen for illustrating the mode amplitude profiles of the Ex-component, while arrows indicate the electric field vectors at a representative moment of time.

Fig. 2. (a), (b) Numerically calculated complex reflection coefficients as a function of the slot antenna’s lateral dimensions at the design wavelength of λ=785nm upon TM polarization. The amplitude |rxx| is visualized by the color map, while the dashed blue lines are the contours of the reflection phase φxx ascending by (a) a 20-deg phase step and (b) a 10-deg phase step. The SiO2 spacer thickness is set to ts=50nm in (a) and ts=10nm in (b). (c), (d) Cross-sectional electric field distributions in different cutting planes for the slot antenna at λ=785nm. The selected cutting planes display the mode profiles within the center of the slot antenna in the top Au layer. The color bars are chosen for illustrating the mode amplitude profiles of the Ex-component, while arrows indicate the electric field vectors at a representative moment of time. (c) The SiO2 spacer thickness is set to ts=50nm and the slot-antenna dimensions are Lx=40nm and Ly=150nm. (d) The SiO2 spacer thickness is set to ts=10nm and the slot-antenna dimensions are Lx=150nm and Ly=230nm.

Fig. 3. Theoretical performance of the beam-steering MCSA metasurfaces that reflect the normal incident TM-polarized light into the +1 diffraction order for supercells consisting of (a) pair, (b) triple, and (c) quadruple identical MCSA meta-atoms. The left columns display the simulated diffraction efficiencies of different orders as a function of wavelength. The right columns show the electrical field distributions at the x–y plane cut from the center of the top slot-antenna layer at the wavelength of λ=785nm.

Fig. 4. (a) Schematic illustration of the MCSA reflective metasurface for beam steering. (b) SEM images of the fabricated beam-steering metasurface. The lower image depicts the fabricated supercells. (c) Simulated (solid lines) and experimental (dots with error bars) diffraction efficiencies of different orders as a function of wavelength for TM incident light. The error bars denote the standard deviation of the measured data of four metasurface samples. The inset image shows the diffracted light spots at λ=790nm, whose intensity has been adjusted for the visualization.

Fig. 5. (a) Schematic illustration of the MCSA reflective metasurface for beam splitting. (b) SEM images of the fabricated beam-splitting metasurface. The lower image shows the designed and fabricated supercells. (c) Simulated (solid lines) and experimental (dots with error bars) diffraction efficiencies of different orders as a function of wavelength for TM incident light. The error bars denote the standard deviation of the measured data of four metasurface samples. The inset image shows the diffracted light spots at λ=790nm, whose intensity has been adjusted for the visualization.