Extraordinary infrared transmission through a periodic bowtie aperture array.

The discovery of extraordinary transmission through periodic aperture arrays has generated significant interest. Most studies have used circular apertures and attributed enhanced transmission to surface plasmon polariton (SPP) resonances and/or Rayleigh-Wood anomalies (RWA). Bowtie apertures concentrate light and have much longer cutoff wavelengths than circular apertures and can be designed to be strongly resonant. We demonstrate here that the total transmission through a bowtie aperture array can exceed 85% (4x the open area). Furthermore, we show that the high transmission is due to waveguide modes as opposed to the commonly believed SPP/RW phenomena. This work is focused on IR wavelengths near 9 microm; however, the results are broadly applicable and can be extended to optical frequencies.