Interaction of terahertz electromagnetic field with metallic grating:   Near-field zone
  We have developed theory for the interaction of THz radiation with a sub-wavelength metallic grating. The structure of electric fields of the electromagnetic wave under the metallic grating has been studied in the near-field zone. Spatial distributions of the electric field components and the electric energy density have been obtained for the transmitted wave through the grating. An effect of strong local enhancement of the electric field has been detected. Spatial dependences of the polarization of the transmitted wave has been analyzed for the near-field zone. 
Yu. M. Lyaschuk and V. V. Korotyeyev
cond-mat.mes-hall physics.optics