Raman lasers (review)

A review is given of the investigations of the properties and characteristics of Raman lasers, i.e., of oscillators and amplifiers using stimulated scattering, and of the associated processes and phenomena. The physical principles and characteristics common to Raman lasers are considered. These principles underlie various processes such as the stimulated Raman scattering, stimulated Brillouin scattering, stimulated Raman scattering accompanied by spin flip, etc. The special features of the dynamics of Raman oscillators and amplifiers are described. New properties of the stimulated scattering, typical of the "wide-band" pumping (spectrum of the exciting radiation wider than the spontaneous scattering line), are discussed. These new properties include the directional asymmetry of the gain and the threshold nature of the dependence of the gain increment of the pumping intensity. The results are given of experimental studies of the use of stimulated Raman and Brillouin scattering in the formation of light pulses, including their lengthening from tens of nanoseconds to several microseconds (Raman scattering) and Q switching (Brillouin scattering).