The development of terahertz sources and their applications.
The terahertz region of the electromagnetic spectrum spans the frequency range between the mid-infrared and the millimetre/microwave. This region has not been exploited fully to date owing to the limited number of suitable (in particular, coherent) radiation sources and detectors. Recent demonstrations, using pulsed near-infrared femtosecond laser systems, of the viability of THz medical imaging and spectroscopy have sparked international interest; yet much research still needs to be undertaken to optimize both the power and bandwidth in such THz systems. In this paper, we review how femtosecond near-infrared laser pulses can be converted into broad band THz radiation using semiconductor crystals, and discuss in depth the optimization of one specific generation mechanism based on ultra-fast transport of electrons and holes at a semiconductor surface. We also outline a few of the opportunities for a technology that can address a diverse range of challenges spanning the physical and biological sciences, and note the continuing need for the development of solid state, continuous wave, THz sources which operate at room temperature.
Davies
A G
AG
Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK. agd11@cam.ac.uk
Linfield
E H
EH
Johnston
M B
MB
D003461:Crystallography / Q000295:instrumentation / Q000379:methods; D003952:Diagnostic Imaging / Q000295:instrumentation* / Q000379:methods / Q000639:trends; D055590:Electromagnetic Phenomena / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D007834:Lasers; D008872:Microwaves; D055095:Optics and Photonics / Q000295:instrumentation; D011840:Radiation, Nonionizing; D012542:Scattering, Radiation; D012666:Semiconductors; D013057:Spectrum Analysis / Q000295:instrumentation* / Q000379:methods; D014159:Transducers