We show that the extraordinary transmission of light through an array of square subwavelength holes is strongly influenced by the size of the holes. For small, square holes (air fraction below 20%), the dependence of the normalized transmission (transmissivity) on hole width greatly exceeds the expectations on the basis of conventional aperture theory. For larger holes, the transmissivity saturates. Moreover, the positions of the transmission maxima shift when the size is varied.
van der Molen, K. L., Segerink, F. B., van Hulst, N. F., & Kuipers, L. (2004). Influence of hole size on the extraordinary transmission through subwavelength hole arrays. Applied physics letters, 85(19), 4316-4318. https://doi.org/10.1063/1.1815379