plate has been crucial for the development of plasmonics, which is now a central part of nanophotonics technology, opening new avenues toward high performance devices such as color filters [1] and sensing platforms. [2] However, a typical drawback of EOT hole arrays compared to other 2D structures such as metasurfaces [3] is the relatively large number of holes necessary to get a well-defined resonance peak with high amplitude. [4] Indeed, this strong dependence of EOT on the number of holes was identified since the first experiments dealing with the phenomenon [5] and was explained invoking surface plasmons. Experimental results at infrared [5] already showed noticeable differences between large and small arrays. More systematic studies dealing with the enhancement of transmission as the size of the array was gradually increased were reported in the millimeter-wave regime [4,6,7] and it was found that with 961 holes (31 × 31) total transmission was reached. [7] Afterward, theoretical [8] and experimental [9] works arrived at the same conclusion.It is nowadays well established that the EOT resonance in subwavelength hole arrays (and also in an aperture flanked by periodic corrugations as discussed later) relies on surface electromagnetic modes that arise due to the coupling between holes (whose shape and size modulate slightly the EOT peak as long as the holes remain subwavelength, i.e., cut-off regime [4,7,[10][11][12][13][14][15] ), regardless the precise origin of these surface modes. [16][17][18][19][20][21][22][23][24] In real metals at visible frequencies, coupling is possible through surface plasmon polaritons as well as diffraction modes. [22] In contrast, metals at terahertz are generally considered as good conductors, and they fit in a high conductivity model which is a good approximation to a perfect conductor. In this regime, surface plasmons cannot be supported and all the coupling is through diffraction. [19] Then, the surface modes responsible for the coupling are leaky waves, [17,22,23,[25][26][27] i.e., complex waves [27] that radiate power away from the surface as they propagate along it. Leaky waves were already invoked in the prominent work by Ulrich [26] to explain the salient features of metal meshes in the far infrared, principally strong peaks in the transmittance that are directly related to the so-called resonant Wood's anomalies of reflection gratings [17,25,26] and that emerge as a result of the interference between the direct beam and the leakage beams.Aside from this, other models have been proposed to explain EOT, which can be classified into three main frames: (i) theory based on surface plasmons, [5,16,18] and (ii) full-wave diffraction models [8,17,19,24,28] discussed above, and (iii) theory based on The discovery of extraordinary optical transmission (EOT) through patterned metallic foils in the late 1990s was decisive for the development of plasmonics and cleared the path to employ small apertures for a variety of interesting applications all along the electromagnetic spectrum....