Although all dye lasers share the same active medium, they differ widely in internal structure. The differences reflect both the choice of pump source and the intended applications of the laser.

The pump source strongly influences design of a dye laser because of the energy-transfer kinetics of the dye. The upper laser level has a lifetime of a few nanoseconds, making the pulsed dye laser a high-gain high-loss system when it is pumped by pulses with high peak power. Pumping is more difficult with a continuous-wave laser which does not generate high peak powers in pulses. To reach the high power densities needed to exceed laser threshold, the moderate power beam from a continuous-wave pump laser must be focused very tightly, concentrating its power in a small volume. Even so, the continuous-wave pumped dye laser remains a low-gain low-loss system. Modelocking and/or cavity dumping allow a continuously pumped dye laser to generate pulsed output.

Flashlamp-pumped dye lasers come with integral flashlamps, and plug directly into a source of electrical energy. On the other hand, most laser-pumped dye lasers are packaged separately from the pump lasers needed to drive them. This arrangement gives users the flexibility to pick the pump source best suited to their needs, within certain limits. (A pulsed pump laser cannot be used with a dye laser designed for a continuous-wave pump laser, and vice versa.) It also meets the economic need to minimize prices, and allow customers to use dye lasers with existing equipment. The...