Generation of THz radiation: Metallic metamaterial grating versus lamellar grating

The Smith-Purcell radiation (SPR) in metallic metamaterial grating is studied theoretically. This metallic metamaterial is a one-dimensional array of slits with sub-wavelength period perforated on a perfect metallic film, which supports discrete guided modes in presence of convective electron bunch near its surface. It is also found that SPR intensity is enhanced when guided modes couple with diffraction mode. The comparison with lamellar grating shows that the metamaterial grating is more effective converter of evanescent field associates with running charge into radiation. This structure would be promising to develop intense narrow-band Smith-Purcell radiation based THz sources.