Laser dyes are large organic molecules with molecular weights of a few hundred mu. When one of these organic molecules is dissolved in a suitable liquid solvent (such as ethanol, methanol, or an ethanol-water mixture) it can be used as laser medium in a dye laser.  Laser dye solutions absorb at shorter wavelengths and emit at longer wavelengths. Successful laser dyes include the coumarins and the rhodamines. Coumarin dyes emit in the green region of the spectrum while rhodamine dyes are used for emission in the yellow-red. The color emitted by the laser dyes depend upon the surrounding medium i.e.the medium in which they are dissolved. However, there are dozens of laser dyes that can be used to span continuously the emission spectrum from the near ultraviolet to the near infrared.
Partial list of laser dyes
- Coumarin (in various nomenclatures such as Coumarin 480, 490, 504, 521, 504T, 521T)
- polyphenyl ("polyphenyl 1")
- Rhodamine 6G
- Rhodamine B
- Rhodamine 123
- Umbelliferone (also known as 7-hydroxycoumarin)
- F. P. Schäfer (Ed.), Dye Lasers, 3rd Ed. (Springer-Verlag, Berlin, 1990).
- F. J. Duarte and L. W. Hillman (Eds.), Dye Laser Principles (Academic, New York, 1990).
- F. J. Duarte, Tunable Laser Optics (Elsevier-Academic, New York, 2003) Appendix of Laser Dyes (includes more than 50 laser dyes)
- S. C. Guggenheimer, A. B. Petersen. "High Power Operation of a CW Ultraviolet Dye Laser". "Prior to 1988, only one laser dye, polyphenyl 1, had been shown to operate CW at wavelengths less than 400 nm."