Line shape enhancement and broadening effects in dye laser intracavity absorption

Abstract

Questions about the line shape of spectral absorption features observed by dye laser intracavity absorption (ICA) have been discussed in the literature for several years. Simple line shapes have been observed as well as complex line shapes exhibiting asymmetry and enhancement wings. Attempts have been made to interpret these line shapes in terms of various models of ICA with varying degrees of success. The study of these line shapes has been under way for some time in our laboratory with attempts being made to observe the true shape of the absorption features in conditions where they will not be masked by instrumental effects. The results are that the type of line shape observed depends on the degree to which the laser is perturbed by the absorber. If the absorber is strong, i.e., either high density or large oscillator strength, the ICA line shape tends to broaden and develop enhancement wings. If, on the other hand, the absorber is of low density or small oscillator strength, the observed line shape tends to be simple. The line shapes tend to become asymmetrical due to index of refraction effects. Line shapes observed in a variety of experimental conditions are presented, and some results are interpreted in terms of a model of ICA.