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What is an argon-ion laser?


Ion lasers consist primarily of lasers operating using ionoised species of the noble gases argon, krypton or xenon. Argon with strong emissions in the visible blue green and weaker lines in the ultra violet and infra red is the most important type commercially. The attraction of the argon-ion laser is the ability to produce CW (continuous wave) output from mW to tens of W in the visible part of the spectrum. The technology however, is fairly complex as can be seen from the schematic representation in Fig.1.

Fig. 1 Argon ion laser schematic
Fig. 1 Argon ion laser schematic

Argon-ion lasers operate in high temperature plasma tubes with bores about 1.2mm diameter, and lengths up to 1.5m. Excitation is by a high current discharge that passes along the length of the tube, concentrated in the small bore. High current density in the centre of the tube ionises the gas and provides the energy to excite the ion to the lasing energy levels. The high current density leads to sputting of the bore materials by the plasma, which is generally detrimental. Extra gas is needed to replenish gas depleted during operation and the low efficiency (~0.1% wall plug) requires methods of removing waste heat. Solutions to these problems use high temperature ceramics, tungsten, separate gas flow paths and active cooling. In addition, magnetic fields are sometimes used to help conform the discharge current to the centre of the bore.

Fused silicon or crystal quartz are usually used for the optics on these lasers, quartz being used for high power visible and UV applications.

Typical values for beam diameters for argon ion lasers are from 0.6 to 2mm with beam divergences of 0.4 to 1.2 mradians.

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