Electromagnetic performance of single-layer and MLCGP metasurfaces. (a) Reflection loss of single-layer metasurfaces with different thicknesses at l = 0. Reflection loss of a 2 mm-thick single-layer metasurface at (b) l = −3 and (c) l = −5. Reflection loss of a 3 mm-thick single-layer metasurface at (d) l = −3 and (e) l= −5. (f) Schematic diagram of the MLCGP metasurface structure. Reflection loss of the MLCGP metasurface at (g) l = −3 and (h) l = −5. (i) Effective absorption bandwidth before and after cascading.