Mode Conversion in Cylindrical Waveguides Using Metasurfaces

A general method to convert between azimuthally-invariant TM
_0n
cylindrical waveguide modes using metasurfaces is presented. Mode conversion is achieved by a metasurface comprising cascaded electric impedance sheets that vary radially. The metasurface is described by a modal scattering matrix that relates the incident and reflected modes on both sides of the metasurface. The sheets' impedance profiles of the metasurface are designed to realize stipulated modal scattering matrix entries. As an example, a mode splitter that divides the power of an incident TM
₀₁
mode evenly between TM
₀₁
and TM
₀₂
modes is reported at 10 GHz. The method presented can be used to design metasurfaces that arbitrarily transform wavefronts in both amplitude and phase.