Transients and instabilities in fir lasers

This paper discusses the principles of operation of a far-infrared laser. The long-time transient associated with the vibrational bottleneck effect is discussed. The authors proceed in the theoretical description of the laser and provide background in which the laser transients are investigated either in a two-level model, which is shown to provide a valid description of the buildup of laser action, or in a three-level model, which is required to describe the laser switch-off. The situations in which no stable steady state corresponds to the operating conditions are considered