MODERN ASPECTS OF FAR-INFRARED GAS-LASERS

A short survey is presented on the recent development of optically pumped pulsed far-infrared (FIR) or THz gas lasers. This includes the new distributed-feedback (DFB) and helical-feedback (HFB) FIR gas lasers as well as the subnanosecond-single-pulse FIR gas lasers pumped by 50 ns 10 mu m pulses of hybrid CO2 lasers truncated within ca. 10 ps at their maximum by a novel ultrafast laser-triggered plasma shutter. These lasers show interesting phenomena such as standard and swept-gain superradiance as well as anticorrelated oscillations of the far-infrared emission and the 10 mu m pump radiation in the Raman regime. In this context it was discovered that FIR laser gases, e.g. CH3F, NH3, D2O, CH3CN, can be used successfully as spectral filters in ''Optical-Free-Induction-Decay'' 10 mu m CO2 laser systems instead of the standard hot CO2 gas. Finally, the single ultrashort FIR pulses are presently applied to FIR or THz quantum-well detectors and to high-T-c superconductors to gain further information on their exciting and complicated features.