Laser dye stability

A figure-of-merit (FOM) consisting of the initial laser slope efficiency times the dye lifetime constant is used to compare the effect of a Pyrex light filter and the cover gas upon the output characteristics of six laser dye solutions. The FOM is found to improve using the Pyrex filter from 2-fold (coumarin 102 under air) up to 3800-fold (rhodamine 6 G under argon). In most cases, the use of argon in place of air for a coumarin dye not only improves the laser output, but also increases the lifetime constant. However, two of the coumarin dyes had an increase in lifetime under air as compared to under argon. This difference is explained in terms of the relative energy levels of the singlet and triplet states of these dyes. In order to measure long-lived dye solutions, a separate output-monitored linear flashlamp was used to degrade the solutions. The dye lifetime constants were corrected for changes in the output of this linear flashlamp. The relative output of this dye degradation flashlamp was found to depend upon the wavelength of the measurement and the position of the sensor along the length of the lamp. The variation in the output of several flashlamps is shown for lamps operating up to a total of 30 million flashes. The lifetime constants of the dye LD-490 measured by using the coaxial laser flashlamp was found to be comparable with, but lower than, the constants obtained from using the linear dye-degradation flashlamp.