Principles of Dye Laser Operation

Abstract

Dye lasers entered the scene at a time when several hundreds of laser-active materials had already been found. Yet they were not just another addition to the already long list of lasers. They were the fulfillment of an experimenter’s pipe dream that was as old as the laser itself: To have a laser that was easily tunable over a wide range of frequencies or wavelengths. Dye lasers are attractive in several other respects: Dyes can be used in the solid, liquid, or gas phases and their concentration, and hence their absorption and gain, is readily controlled. Liquid solutions of dyes are especially convenient: The active medium can be obtained in high optical quality and cooling is simply achieved by a flow system, as in gas lasers. Moreover, a liquid is self-repairing, in contrast to a solid-state active medium where damage (induced, say, by high laser intensities) is usually permanent. In principle, liquid dye lasers have output powers of the same magnitude as solid-state lasers, since the density of active species can be the same in both and the size of an organic laser is practically unlimited. Finally, the cost of the active medium, organic dyes, is negligibly small compared to that of solid-state lasers.