Fig. 1. (a) Schematics illustrating the principle and structural design of a metasurface. A uniform planar wave with right circular polarization is irradiated on the metasurface of spatial structural changes, the emitted light field will therefore carry varying amplitude and polarization in space. Intensity distribution is different in two orthogonal polarization components, so the patterns detected at different polarization angles will be different as shown in the left graphic. For viewing purpose, two images are staggered in diagram, but in reality, they are in the same position. (b) Front view of part of the metasurface, the nano bars are made of gold with varied sizes and rotations, the substrate is SiO₂ with refractive index n=1.45.

Fig. 2. All possibilities for binary image (0, 1) synthesis. There are four cases for intensity distributions in the x-polarization and y-polarization, namely, (0, 0), (0, 1), (1, 0) and (1, 1).(a, d) show the simulated transmittance for four cases under circularly polarized incidence. Rectangles inserted in the figures represent the corresponding nano bars, which have different sizes or rotations and are optimized for 800 nm to meet the requirements. The thickness of nano bars is 30 nm, and the period is 300 nm.

Fig. 3. Vector composition diagram of binary images.(a, b) Binary images with pixel numbers 1024×1024 adopted in the design. (c) Selected vector synthesis diagram corresponding to the yellow region in (a) and (b). The dots, horizontal, vertical and slant arrows represent (0, 0), (1, 0), (0, 1) and (1, 1), respectively.

Fig. 4. Experimental setup for polarized detection.Expander: concave lens with f=-75 mm. Collimation: convex lens with f=200 mm. LP1 and LP2: linear polarizer. QWP: quarter wave plate. Sample: designed metasurface with effective size approximately 300 μm × 300 μm. Lens: convex lens with f=50.8 mm. CCD: charge-coupled device with pixel numbers 1024×1392.

Fig. 5. Experimental results of polarization detection.(a) The simulated and experimental results of images without polarizer, the intensity profile is the superposition of two images. (b) The simulated and experimental results of images with polarizer along the horizontal and vertical directions, respectively. (c) Experimental results at 0°, 30°, 45°, 60° and 90° by gradually rotating the analyzer, the pattern gradually transformed from plum blossom to lotus. (d) SEM image of the fabricated metasurface. The scale bar is 500 nm.