The terms "three-level-system" and "four-level-system" are in wide use, as are the terms "quasi-three-level," etc. [1]. The introduction of a "level parameter," e, that varies continuously from two to four facilitates a quantitative comparison of laser media, operating temperatures, and choice of pump (λ_P) and laser (λ_L) wavelengths. We propose two parameters, e_0 and e_1, with values close to three for a system that would commonly be called three-level, and close to four for many systems that would commonly be called four-level.
展开▼
