The influence of grating profile on surface plasmon polariton resonances recorded in different diffracted orders

Nonlinear processes involved in the manufacture of nominally sinusoidal sur face relief diffraction gratings can introduce distortions into the profile of these surfaces. Such distortions may dramatically affect both the specu lar reflectivity and diffracted efficiencies from such a surface, particula rly if it is metallic. To illustrate this a comprehensive numerical modelli ng study of the optical coupling to surface plasmon polaritons on silver gr atings has been undertaken. The grating surface profile is represented in t erms of a truncated Fourier series, the effect of varying the amplitude, an d then the phase, of each Fourier component in turn, is explored. This illu strates the sensitivity of individual features to specific harmonic compone nts of the surface, for surface plasmon resonances recorded in both the zer oth and higher diffracted orders.