Directions in TeraHertz technology

The term 'T-rays' was coined in the early 1990's by Bell Labs to describe the spectrum in the TeraHertz range (1 THz= 10(12) Hz). The THz region of the spectrum lies on the border of where electronics and optics meet, between the mm-wave and infrared bands. Infrared sources become very dim as we approach the THz region and high speed devices struggle to reach these frequencies. Consequently, practical 0.1 THz to 20 THz sources were difficult to obtain until recent developments in laser, quantum well and compound semiconductor technology in the 1990's. Historically, we know that each time a new band in the electromagnetic spectrum opens up, a whole new industry develops and revolves around that band.