The simulated (dashed lines) transfer functions along the x axis for the conventional single-lined gratings and the simulated (solid lines) and experimentally measured (circles) transfer functions for our inverse-designed metasurfaces. The colour of the plots corresponds to the red, green and blue wavelengths. The designed metasurfaces are much more efficient than conventional gratings in green and blue, but, due to the very large diffraction angle of red, further improvement of the efficiency of the red channel is more difficult.
