Principle of MBSW generation: the two-beam case. A binary linear surface-relief grating defined by period d, ridge width c, and ridge height h on the bottom of a substrate of thickness H splits the input beam into two diffracted orders m = −1 and m = +1, which excite BSWs on the top surface of the substrate by interaction with the multilayer stack (ML). We assumed n_sub = 1.462 and n_sup is air.