Electromagnetic Response of Finite Terahertz Metafilm Arrays Excited on Total Internal Reflection Boundaries

Resonant excitation of planar terahertz metamaterials using attenuated total reflection is demonstrated. Experimental results reveal an anomalous increase in the resonance strength while the sample is illuminated near the edge of the metamaterial array with a finite-size terahertz beam. A re-radiation signal at the fundamental metamaterial resonance is observed on the transmission side of the total internal reflection interface where no signal was expected. Multiple theoretical approaches address the physical origins of this re-radiation signal and rich behavior has been simulated with numeric simulations. Although models indicate that surface waves could exist, radiation coupled across the total internal reflection surface appears predominately mediated by finite currents oscillating in resonators at the edge of the metafilm array. The observations could lead to a better understanding of boundary effects in finite, planar metamaterials and more accurate modeling of MM-mediated total reflection spectroscopy.