Novel complementary metasurfaces for the orbital angular momentum generation

Besides amplitude, phase and polarization, wavefront is an important property of electromagnetic (EM) waves. EM waves with twisted wavefronts are known to carry orbital angular momentum (OAM). In this paper, a complementary-type metasurface is proposed to generate an OAM beam at microwave regime. Two metasurfaces that can produce OAM of order 2 and 4 are designed. By using our novel design methods, which are based on circuit model and dyadic Green's function, a high conversion efficiency has been achieved with a very low profile.