Modeling of collisional energy transfer in optically pumped far infrared lasers

Optically pumped far infrared (OPFIR) lasers have been the subject of extensive theoretical and experimental investigations. A detailed review of this work has been published recently (1). Although many important aspects of these lasers are now well understood, comprehensive modeling of these lasers is very difficult because of the large number of states that influence the lasing and because of potentially nonlinear and inhomogeneous effects of the pump laser. Consequently numerous approximations and simplifications have been required to obtain tractable analytic models. An additional complication has been a lack of the requisite extensive experimental data needed to guide the development of these models. The net effect has been models that extrapolate poorly into new operating regimes (e.g. pump intensity and pressure) and derived parameters that are related to actual physical processes in complicated or unknown ways.