Single-frequency operation of argon ion lasers

An expression is derived for the gain coefficient of a laser mode sustained by excited ions produced in a dc gas discharge. Included in the derivation are the effects of the left-right gain asymmetry introduced by ion drift. From this expression, laser power versus frequency curves are obtained which are fit to experimental data obtained on the 4880-Å and 5145-Å transitions of singly ionized argon. From the curve fitting procedure, radiation interaction widths and saturation intensities for the transitions are determined. In addition, it is shown that the fraction of population inversion utilized during single-frequency operation of these lasers can be quite large.