Prism coupling to terahertz surface plasmon polaritons

Silicon prisms are used to couple free-space broadband terahertz into surface plasmon polariton (SPP) modes, otherwise known as surface electromagnetic waves (SEW) or Zenneck waves, on to polished metal surfaces. We show that coupling to surface waves occurs via edge-diffraction and hump-coupling and that attenuated total reflection is not an important coupling mechanism. Coupling and decoupling to a broadband, single-cycle SPP pulse is demonstrated with an energy efficiency of approximately 3.5%. Measurements of SPPs through thin plastic films reveal a strong surface sensitivity and suggest new configurations for maximizing THz SPP utility.