We present measurements and a numerical modeling that elucidate the role of surface plasmons in the resonant transmission of a subwavelength slit in a conducting material. By using THz time domain spectroscopy, we determine the Fabry–Pérot transmission resonances for a single slit formed from a wafer of a semiconductor with a surface plasma frequency in the THz frequency range. We measure large redshifts in the resonant frequencies close to the surface plasma frequency, which are 50% lower than the resonance frequencies expected well below the surface plasma frequency. This is an effect attributed to the coupling of plasmons on the adjacent surfaces of the slit.

Phys. Rev. B

Isaac, T. H., Gómez Rivas, J., Sambles, J. R., Barnes, W. L., & Hendry, E. (2008). Surface plasmon mediated transmission of subwavelength slits at THz frequencies. Phys. Rev. B, 77(Article number: 113411), 1–4. doi:10.1103/physrevb.77.113411