Terahertz (THz = 1012 Hz) radiation encompasses frequencies invisible to the naked eye in the electromagnetic spectrum, lying between microwave and infrared. Until recently bright sources of terahertz radiation and sensitive means of detection did not exist and this region of the spectrum became known as the 'terahertz gap'.
This region of the spectrum has many potential applications in the security and pharmaceutical industries, it is intrinsically safe, non-invasive and non-destructive. Combined with this, many chemicals have unique spectral fingerprints at these frequencies.
The Semiconductor Physics group at the Cavendish Laboratory has played an important role in the development of research in this area. We have applied our knowledge of semiconductor growth and device fabrication to undertake the following:
- Development of broadband sources and detectors of THz radiation using low temperature grown GaAs and InGaAs.
- The growth of the first quantum cascade laser (QCL) in the THz regime.
- The first demonstration of continuous wave operation of a THz QCL.
- Studies of the reproducible growth of THz QCL active regions over a wide range of frequencies.
- Terahertz transfer onto a telecom optical carrier.
This work has involved collaborations with the Universities of Pisa, Neuchatel and Paris as well as Teraview, a University of Cambridge spin-off company which has made considerable progress in developing applications of Terahertz radiation.