Capture of a terahertz wave in a photonic-crystal slab

With many potential applications in mind, great effort is being applied to develop a terahertz-wave technology platform on which waves can be manipulated with sufficient confinement and efficient interaction for the development of smart components. Here, we utilize the in-plane resonance of a thin, planar photonic-crystal slab with negligible absorption loss to successfully demonstrate and visualize terahertz-wave trapping. We artificially introduce free carriers, which interact with the trapped waves, and capture them in the slab by absorption. Our system exhibits an experimental absorptivity (interaction efficiency) of similar to 99% and a broad bandwidth (absorptivity of >= 90%) that covers 17% of the centre frequency. We also demonstrate its application to the stabilization of terahertz wireless communication systems. Our study shows the capability of photonic crystals as a terahertz-wave platform, the application of which may be extended to other components including filters, couplers, antennas, detectors, modulators, switches and emitters.