“…Transmission through a metal screen with subwavelength-sized holes, however, can be drastically increased. This is so-called extraordinary optical transmission [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. To understand the physics underlying this phenomenon, Porto et al [ 3 ] studied the transmission of two-dimensional gratings and found that the capability to control the free electrons on the metal surface was driven by the ability of the alternating incident electric field to collectively oscillate as surface plasmons.…”