The terahertz gap: into the dead zone
New materials are opening up applications for terahertz radiation in the physical, biological and medical sciences. Joe McEntee reports
The terahertz (THz) region of the electromagnetic spectrum is sometimes called the dead zone between electronics and optics - and for good reason. With outer limits generally taken to be 300 GHz to 10 THz (10x 1012 Hz), THz radiation corresponds to a wavelength range between about 1 and 0.03 mm. At lower frequencies lies the electronic regime of millimetre or microwave radiation, used for applications such as wireless telecommunication.
At higher frequencies lies the optical regime, where active optical devices like semiconductor lasers and light-emitting diodes generate near-infrared and visible light for fibre-optic transmission and data storage. Between these two worlds lies the THz technology gap, where conventional solid-state optical and electronic technologies simply don’t measure up. Until just a few years ago, generating and detecting THz radiation was extremely difficult, holding enormous promise yet tantalisingly out of reach.