Transmission properties of terahertz pulses through an ultrathin subwavelength silicon hole array

We demonstrate extraordinary THz transmission of an array of subwavelength apertures patterned on ultrathin highly doped silicon by reactive ion etching. The zero-order transmission spectra exhibit well-defined maxima and minima which are attributed to the excitation of surface-plasmon polaritons and Wood's anomaly. The transmission anisotropy is investigated with respect to the orientation of the elliptical hole array in the frequency range from 0.2 to 3.5 THz, and we notice that the transmission increases significantly when the major axis of the elliptical hole is perpendicular to the polarization of THz beam. In addition, redshift and reduction in transmission amplitude are observed when the surrounding dielectric permittivity is increased.