Microstructured terahertz waveguides

Research involving the tetrahertz (THz) part of the electromagnetic spectrum, commonly taken to be the region between 0.1 and 10 THz (3 mm to 30 µm), has seen rapid growth in recent years because of the importance of THz radiation as a low energy probe of the optical properties and dynamics of matter and partly because of emerging real world applications in areas as diverse as industrial quality control, biosensing and security screening. Despite a vigorous growth in THz technology, many components and processes taken for granted at higher and lower frequencies are still in an early stage of development. One example of this is the use of waveguides to transport or spatially confine radiation. In this review we summarise progress in developing THz waveguides, paying attention to the role that microstructuring on a sub-wavelength length scale can play in engineering new capability and the various trade-offs between loss, bandwidth, group velocity dispersion and spatial confinement.