Carbon Dioxide Laser Instrumentation
The C02 laser’s energy is supplied by passing an electrical current (DC) through a mixture of helium, nitrogen, and carbon dioxide (this is in contrast to the ruby laser, which is excited by powerful flash lamps) that is contained in a cylinder with reflective mirrors at the end known as an optical cavity. The mirrors are aligned in such a manner as to have a common optical axis, whereby if a photon strikes one mirror it will be reflected to the second mirror and return in a similar fashion. Each pass through the optical cavity may result in photon absorption and yield stimulated emissions. In a short time, a population inversion and a laser effect are achieved. If a small optical opening is created in one mirror (i.e., a semitransparent mirror) a stream of photons that has the unique properties of being parallel and of the same frequency will exit. The energy density in the beam cross section is extremely high, and if this energy is passed through a lens system of appropriate material, an even greater cross-sectional density of energy can be achieved at the focal point. Using a system of gimbaled mirrors outside the optical cavity and on appropriate lens, the carbon dioxide laser has been harnessed for precision surgery (Fig. 2.1).
KeywordsLaser Beam Power Density Spot Size Transverse Mode Optical Cavity
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