Bethe's aperture theory for arrays

Bethe's theory is applied to the optical transmission through an array of apertures in an infinitely thin perfect electric conductor. This method shows that, in the small-aperture limit, the lowest-order TM evanescent mode governs the transmission process, allowing for both 100% transmission at the passband wavelength and zero transmission at the Wood's anomaly. The applicability of this theory to total transmission in other systems is discussed, and a specific example of a single aperture in a transverse screen of a rectangular waveguide is given.