Terahertz mirror is omnidirectional and broadband

Though terahertz technology is receiving most attention for its homeland-security applications in checking people, mail, or luggage, it also has applications in short-range free-space communications. For this particular use, a high-quality mirror operating in the terahertz region with a reflection band tailored to match the carrier frequency of the communications system could ensure a reliable link even in a crowded office environment. Although polymer dielectric mirrors operating in the terahertz region have been demonstrated, researchers at Technische Universität Braunschweig (Braunschweig, Germany) and Rice University (Houston, TX) have developed an improved mirror with higher reflectivity and a broader reflection band that is also omnidirectional (highly reflective for all incidence angles).

To achieve the omnidirectional function, the researchers sandwiched four layers of 63-µm-thick silicon (with a refractive index of 3.418) between five 150-µm-thick layers of polypropylene (with an index of 1.53) to construct the mirror. Transmission and reflection measurements from a fiber-coupled terahertz time-domain spectrometer showed high reflectivity for all incidence angles and for s and p polarizations for frequencies between 319 and 375 GHz. Contact Norman Krumbholz at n.krumbholz@tu-bs.de.