Advances in Terahertz Technology with Emphasis on Quantum Cascade Lasers

Starting from the year 2002 when the development of quantum cascade lasers shifted from mid-infrared to the terahertz domain, the remarkable rise in the terahertz research has followed. The paper discusses the recent achievements in development of the terahertz radiation sources with emphasis on quantum cascade lasers. Moving towards the higher working temperatures, longer wavelengths and higher output power is discussed.