The dye laser is an optically pumped laser, with
an organic dye in a liquid solvent as
the lasing medium. It consists of a dye lasing chamber
with a normal mirror in one end and a semitransparent
in the other. Since it is an optically pumped laser
it has an external lightsource (usually a xenon tube or an air
flash tube). When the flash tube is triggered, the photons
will fly through the liquid and stimulate the dye to emit
photons . Some of these will be reflected by the mirrors, and
move back through the chamber. This stimulates further emissions.
The light will eventually leave the chamber through the semitransparent
mirror as the beam.
Simple buildup diagram of a dye laser:
From dye Flow-back
circulation to
pump liquid storage
||| |^|
Mirror|v| Reflector |||
| | ================== | |
|.--' `--------------------' `----.| Beam
|| laser chamber |::::::::::::::::::
|| |::::::::::::::::::
|`--------------------------------'|
Semitransparent
.---------------------. mirror
-| Xenon tube |-
`---------------------'
The dye is rapidly broken down from the lasing proccess,
so a circulation system is used to prolong the possible lasing
time. This system, pumps in new liquid from an external
storage tank.
Due to the need for replenishment of the dye liquid and the
need for an external tank this laser type is rather impractical,
compared with the Laser diode, the HeNe-laser and
the Ion laser, and is only used in experiments. Most of
the organic dyes used in this laser type are toxic.
One advantage with this laser is that by changing
the dye used, you can get most light frequencies. | 
