Bragg reflection of THz surface plasmon propagating over a diffraction grating

We study the propagation of THz surface plasmon (SP) on flat metal surfaces and we propose an explanation for the unexpected low SP propagation length. Together, we present results of Bragg reflection of SPs at a grating engraved at the metal surface. THz time-domain spectroscopy allows us to identify all the diffractive processes at the grating.