Fundamental Physics of Solid-State Laser-Type Materials

This article on the fundamentals of solid-state laser sources is associated with three other articles on crystalline luminescence applied to laser sources [AF3276] , crystals and nonlinear optics [AF3278] and the generation of short (ns) to ultrashort laser pulses down to the femtosecond (fs) [AF3282] .

Its aim is to introduce the subject of solid-state laser sources and to describe the main physical parameters, mainly optical, needed to understand how they work.

We define the vocabulary for basic concepts such as optical pumping of crystals and glasses doped with active ions, the main elements of a laser source, absorption and emission transitions of active centers, the population of energy levels and particularly 3- and 4-level systems applied to lasers, the Einstein coefficients of absorption, spontaneous emission and stimulated (or induced) emission, absorption and emission cross sections, and the lifetime of an energy level. Finally, for the resonant cavity, we define the intensity emitted by the laser beam, Gaussian beam optics, spectral characteristics, modes and coherence.