Waves on subwavelength metallic surfaces: a microscopic view point

The electromagnetic properties of subwavelength metallic surfaces are due to two kinds of elementary distinct waves, the famous surface plasmon polariton and the quasi-cylindrical wave, which are both scattered by the subwavelength indentations as they propagate on the metal. The ab-initio microscopic description of the electromagnetic properties starting from the sole knowledge of the elementary waves launched in between the indentation has a long history in grating theories. We review the evolution of the ideas and the fundamental principles that govern these waves and their impacts. For the sake of illustration, the emblematic case of a metal surface perforated by a subwavelength-hole array, which exhibits remarkable transmission properties, is taken to illustrate our purpose.