Laser dyes include the coumarins and the rhodamines. Coumarin dyes emit in the green region of the spectrum, whereas 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.