Extraordinary transmission through slits from a microwave engineering perspective

Extraordinary transmission (ET) of light (or electromagnetic waves in general) through periodically perforated metal screens with electrically small apertures has attracted a lot of attention from many researchers working in the fields of optics, solid state physics and microwave engineering. Some controversial explanations have been given to this phenomenon. A relatively simple explanation based on well known concepts coming from waveguide theory has been reported by some of the authors for the case of 2D arrays of small holes. The case of 1D arrays of slits is different because they can support TEM modes at any frequency. This contribution gives satisfactory explanation to many facts observed in the transmission of electromagnetic waves through slits in metal screens using simple modeling and physical interpretation. Apart from providing a new point of view on the ET phenomenon, our explanation is simpler than others and suitable for educational purposes.