Surface-mode lifetime and the terahertz transmission of subwavelength hole arrays

We measure the enhanced transmission of Terahertz radiation through a metal film perforated with arrays of subwavelength holes of varying hole size. By measuring transmission spectra in the time domain and comparing our experimental results to a rigorous modal-matching model, we are able to assess the relative contributions of resonant and nonresonant transmission channels. We see that the contribution of the resonant transmission becomes more important with decreasing hole size because the lifetime of the surface mode mediating the transmission is increased with reducing hole size. Using low-temperature measurements to control the nonradiative loss levels in our system, we show that losses limit the lifetime of the surface mode, thereby limiting the resonant transmission intensity for the smallest holes.