Fig. 3: Fabrication and characterization of the metadevice.

a Optical and scanning electron microscopes (SEM) images of the fabricated all-Si metasurface from different angles. b The experimental measurement setup for performance characterization. Blackbody, a linear polarizer, and liquid crystal retarder are used to generate collimated and the broadband incidence with selected polarization states. A series of commercial bandpass filters with 50–250 nm bandwidths are adopted to produce monochromatic light. The mid-wavelength infrared camera captures the interfered patterns in the far-field cooled at about 80 K. c The captured images at different frequencies on the same focal plane with left circular light incidence. The annular intensity distribution rotates with the incident frequency. d The intensity contrasts at different frequencies. The values are on a logarithmic scale. e The mapping relationship between the rotation angle of the interfered spots and the frequency. The analytical values are also plotted for comparison as indicated by the purple dashed line. The gray zones highlighted in (d) and (e) denote the designed operation bandwidth from 3150 nm to 4150 nm. The blue background in (d) and (e) represents the designed operation bandwidth.