Using a metasurface to detect fractional topological charges at different wavelengths

This paper demonstrates a possibility of detecting fractional topological charges (TC) using a metasurface in the near and far fields. The feasibility of detecting fractional TC at different wavelengths is studied. The light wavelength and TC can be estimated by shifting the light spot along different axes: when the wavelength of light changes, the light spot in the observation plane shifts along the X axis. When the fractional part of the TC changes, it shifts along the Y axis. The metasurface remains usable in the wavelength range from 0.56 to 0.7 μm.