Vector field mapping of THz-electromagnetic wave transmitted through quadruple square holes

By using terahertz (THz) time-domain spectroscopy we measured THz-electromagnetic pulse passing through a two-by -two subwavelength hole matrix in near-field regime. Our Fourier analysis of measured data shows detection position dependent transmission maxima with respect to the polarization direction of the incident field. By comparing with numerical simulations based on finite element method, we found that the frequency dependent coupling between the transmitted waves through individual holes leads to different transmission maxima directly above and between holes.