Changes in the spectral profile of the gain band of a dye solution in an intense narrow-band radiation field and their manifestation in pulsed dye lasers

Three different methods, namely probing the gain of a dye solution with two concurrent collinear beams of intense narrow-band and weak broad-band radiation, transillumination of a dye solution emitting broad-band radiation with a beam of intense narrow-band radiation, and simultaneous laser emission of narrow-band and broad-band radiation from a dye solution were used in order to show experimentally that in an intense narrow-band radiation field a change occurs in the spectral profile of the gain band of excited organic-dye solutions. This consists in a reduction of the gain at the short-wavelength edge and the appearance of additional gain at the long-wavelength edge of a narrow line. The effect changes the spectral composition of the radiation amplified by an excited dye solution and, at high laser output powers, transforms the line emission profile of pulsed dye lasers with selective and nonselective resonators (when their spectral emission characteristics are controlled by external injection).