Optimum areal coverage for perfect transmission in a periodic metal hole array

We investigate the conditions for perfect transmission of terahertz radiation in periodic two-dimensional plasmonic system of square holes. Changing the period in the direction perpendicular to the incident light polarization reveals the optimum areal coverage for perfect transmission at a specific period. The simulated near-zone energy flow distributions show that all incident light is accumulated on the apertures, under the condition that the period is shorter than the resonant wavelength, acting as static local capacitors restricted to a wavelength-confined region. Our finding can be exploited for designing cost-effective terahertz filters and may be applicable to terahertz spectroscopy requiring strong local field enhancement.