Time-of-Flight Model for the Extraordinary Transmission Through Periodic Arrays of Subwavelength Apertures at THz Frequencies

A qualitative model explaining the extraordinary optical transmission of terahertz (THz) radiation through two-dimensional periodic arrays of subwavelength apertures is presented. Systematic terahertz time-domain spectroscopy studies have been undertaken to investigate the combined effects of the lattice arrangement, aperture shape, area and aspect ratio on the transmission properties of electroformed copper arrays. The extensive results presented provide a unified example of how aperture geometry dictates SPP activity. The novel fabrication method creates exemplary peak resonances, allowing the onset of surface plasmon polariton (SPP) decoupling to be distinguished from direct transmission. Furthermore, we provide the first evidence as to how the temporal properties of SPPs are governed by the single-cycle THz pulse. The time-of-flight model presented can not only be used to explain the results observed in both the presented and previously published experiments but serves as a method to engineer specific resonances for sensor applications.