Transmission resonances of electromagnetic wave through metallic gratings: phase and field characterizations.

We investigate experimentally and numerically the transmission resonances of electromagnetic wave through a metallic grating of periodic slits as well as an array of subwavelength holes. The far-field transmission (magnitude and phase) spectra and the detection of surface electric field are used to characterize two kinds of transmission resonances (Fabry-Perot-like and structural factor resonance) occurring to the slit grating. In addition, the comparison between the slit grating and the subwavelength hole array reveals the effect of the aperture property on the phase and field of resonantly transmitted electromagnetic wave.