Equivalent circuit model to explain extraordinary transmission

This work proposes a circuit model based explanation for the extraordinary transmission (ET) of light phenomenon studied in recent scientific literature [1], [2]. ET mainly stands for unexpected transmission of light through periodic arrays of subwavelength holes in a metal screen. The study of this phenomenon has attracted the attention of many scientists working in the fields of Optics and Condensed Matter Physics, giving place to some controversial explanations. The existence of surface plasmons supported by the metal/air interface at optical frequencies has been considered the underlying reason behind ET. Our contribution tries to offer a relatively simple explanation of ET based on conventional waveguide/transmission-line theory. It will be shown how this simplified microwave-engineering standpoint offers satisfactory explanation for most ET findings. Indeed, ET should be expected not only at optical frequencies but also at lower frequencies, when surface plasmons are not possible.