Restrahlen to T-rays - 100 years of terahertz radiation.

Although a reliable source of subpicosecondterahertz (THz) pulses, or T-rays, wasdemonstrated in the late 1980s, it was notuntil 1995, when they were used forimaging, that their full potential wasrealized. However, much of the publicityat that time seemed to suggest that verylittle research had taken place in the THz(or far-infrared) region before then. Withthe - largely new - present-day interest inbiological applications of THz radiation itis apposite to review the opening up ofthis spectral region over the past hundredyears. This paper attempts to show many ofthe significant developments in sources,detectors and spectroscopic systems for theTHz region and includes brief descriptionsof some of the more important applicationsand outcomes of the research.T-rays are only one of a number of verysignificant arrivals on the THz scene inrecent years. It does seem an ideal timeto pursue the exciting biologicalapplications of THz radiation which are tobe discussed at this Workshop.