We have investigated, both theoretically and experimentally, the intensity of p-polarized light diffracted by a metallized diffraction grating when surface plasmons are excited and when they are not. Experiments were made on modulated silver surfaces, and light in the near and far fields was detected by a sharpened optical fiber. Good agreement between experiment and theory (based on the differential method) was found for the intensity collected by the fiber for several angles of incidence in near and far fields. These angles of incidence were chosen to produce amplitudes of the electromagnetic field that displayed many differences in the near-field and far-field zones. The near-field study, both experimental and theoretical, gave us extra information about the sample. Indeed, the near field is composed of evanescent waves, which describe the high spatial frequencies of the surface and thus its subwavelength structures. Analysis of the electromagnetic fields diffracted in far and near fields by the grating permits refinement of the parameters of the sample (thickness of silver) and of its environment (thickness and refractive index of a mixed air–water layer deposited on the sample). Finally, we present and analyze the electromagnetic field diffused by the grating when the surface was oxided after a long period in ambient air.
© 1999 Optical Society of America
L. Salomon, F. de Fornel, and P. M. Adam, "Analysis of the near field and the far field diffracted by a metallized grating at and beyond the plasmon resonance," J. Opt. Soc. Am. A 16, 2695-2704 (1999)