Abstract
A theoretical and experimental study has been made of the small signal gains of six coumarin dyes (DAMC, 4 MU, 7 HC, calcein blue, esculin and scopoletin) in a common solvent (ethanol), and the variation correlated with the different substituents in the coumarins. The relative variation in gain, taking the value for DAMC as the basis, is about 75% for 4 MU, 7 HC and calcein blue, 55% for esculin and 20% for scopoletin. The total tunable range for these dyes is from 430–530 nm. The higher gain in the case of DAMC is attributed to the relatively higher intramolecular charge transfer in this dye compared to the hydroxy-coumarins. The different substituents in the hydroxy-coumarins studied appear to have only a marginal influence on the gain.