Interferometric measurement of the phase of diffracted waves near the plasmon resonances of metallic gratings.

We propose a method for analyzing both theoretically and experimentally the behavior of the phase of the waves diffracted by gratings. The method is applied to the study of resonance phenomena. It is used for determining the optogeometrical parameters of a metallic grating. We show that the experimental setup, which is insensitive to mechanical drifts or thermal fluctuations, can be used for sensing purposes.