The THz domain refers to frequencies of electromagnetic radiation that fall in the range around 10¹² Hz, between mid-infrared and microwave sources. A major limitation historically was that we did not generally have good sources for this region. However, with major advances in the technology, combined with the realization that several novel applications can be anticipated, THz science and technology has attracted rapidly growing attention in recent years. In addition to a variety of fundamental studies which are enabled via THz sources, sectors such as security, biomedical, communications, quality assessment, and environmental monitoring are benefiting from advances in THz technology.

Although there are now several approaches to the generation of THz radiation, one attractive approach, which also offers perspectives for ultrafast pump-probe studies, is based on femtosecond laser sources. This is the basis of THz beams in our laboratory. A schematic of the basic idea behind THz spectroscopy is given below. Using ZnTe and GaAs as emitters we have developed an electro-optic THz system operating at the 1 kHz repetition rate of the Ti:sapphire regenerative amplifier. A typical THz waveform showing the electric field versus time is also illustrated.

To date researchers in the PRL have used THz capabilities in experiments to study carrier dynamics in semiconductors and to determine accurate values of nonlinear optical coefficients. In addition, numerous studies of high-temperature superconductors have been undertaken.

Our group (H.K. Haugen et al) has also been involved in a new initiative at the Canadian Advanced Laser Light Source near Montreal, located on the campus of INRS. Together with many Canadian researchers from a variety of institutions, a very intense THz source was developed. Such sources open the door to qualitatively new science and technology in this area, facilitating for example, nonlinear THz experiments. New possibilities for imaging are also anticipated.