Effect of small damping constant on electric field enhancement at narrow interface in terahertz attenuated total reflection

We investigated surface phonon polariton in cesium iodide with terahertz time-domain attenuated total reflection method. Systematic experiments with precise control of the distance between a prism and an active material directly indicate that the local electric field at the interface considerably enhances with the surface phonon polariton resonance. This is ascribed to the extremely small damping constant of surface phonon polariton compared with the longitudinal-transverse splitting of the phonon modes.