Abstract

Until now cw dye laser action has been observed only when the dye solution flows very fast (10 m/s) through the active region. This is realized mostly by using the jet stream technique. Two reasons for the demand of fast dye flow are generally accepted: first, reduction of thermal disturbances and second, mechanical quenching of the lowest triplet state of the dye molecules. A frequently used and high efficient laser dye solution is Rhodamine 6G in ethylene glycol. Employing a new spectroscopic method, we measured a triplet state lifetime of 5 µsec in air-saturated solution at room temperature.¹ This is to be compared with the dye molecules, flight time through the active region of a typical cw dye laser. This time is about 2µs. Therefore, owing to the motion of the jet, the triplet state population in the active region is reduced sufficiently so that laser action becomes possible. Moreover it was concluded from the triplet data of Rhodamine 6G¹ that no optical gain can be expected in ethylene glycol without mechanical removal of triplet molecules.

© 1994 IEEE