Dye laser

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File:Coherent 899 dye laser.jpg
Close-up of a table-top dye laser based on Rhodamine 6G, emitting at 580 nm (yellow-orange). The emitted laser beam is visible as faint yellow lines. The orange dye solution enters the laser from the left, and is pumped by a 514 nm (blue-green) beam from an argon laser. The dye jet is in the center of the image, behind the yellow window.

A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths. The wide bandwidth makes them particularly suitable for tunable lasers and pulsed lasers. Moreover, the dye can be replaced by another type in order to generate different wavelengths with the same laser, although this usually requires replacing other optical components in the laser as well.

Dye lasers are also used dermatologically, to make skin tone more even.

Construction

Since organic dyes tend to degrade under the influence of light, the dye solution is normally circulated from a large reservoir[1]. The dye solution can be flowing through a cuvette, i.e., a glass container, or be as a dye jet, i.e., as a sheet-like stream in open air from a specially-shaped nozzle. With a dye jet, one avoids reflection losses from the glass surfaces and contamination of the walls of the cuvette. These advantages come at the cost of a more-complicated alignment. Dye lasers emission is inherently broad. In order to produce narrow bandwidth tuning these lasers use many types of cavities and resonators which include gratings, prisms, and etalons[2].

Chemicals used

Some of the dyes are Rhodamine 6G, fluorescein, coumarin, stilbene, umbelliferone, tetracene, malachite green, and others.

Adamantane is added to some dyes to prolong their life.

Cycloheptatriene and cyclooctatetraene (COT) can be added as triplet quenchers for rhodamine G, increasing the laser output power. Output power of 1.4 kilowatt at 585 nm was achieved using Rhodamine 6G with COT in methanol-water solution.

File:AVLIS laser.jpg
An atomic vapor laser isotope separation experiment at LLNL. Green light is from a copper vapor pump laser used to pump a highly tuned dye laser which is producing the orange light.

References

  1. F. P. Schäfer and K. H. Drexhage, Dye Lasers., 2nd rev. ed., vol. 1, Berlin ; New York: Springer-Verlag, 1977
  2. F. J. Duarte and L. W. Hillman, Dye Laser Principles (Academic, 1990)

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