Amplification of spontaneous emission and gain measurement in dye amplifiers

A comparison is reported of the observed spectral narrowing of amplified spontaneous emission from dye amplifiers with predictions from a dynamical model based on rate equations. This is employed to develop a generally applicable method of determining the unsaturated gain within the dye medium. Comparison is made with another technique for determining gain over the restricted pumping range for which it is applicable. The matching of theory to experiment is sufficiently sensitive that good values can also be determined for the wavelength dependence of the excited singlet state absorption cross section.