Four-branch oscillation from a dual-polarization cavity CO2 laser

We report here for the first time multiline oscillation of a cw-CO₂ laser on all the four branches 10P, 10R, 9P, and 9R where all laser wavelengths share a common gain medium. The 9R, 9P and 10R branch lines lased at the expense of the high-gain 10P branch lines for which the cavity offered very high transmission losses. The 10P(20) line was made to lase by constructing another cavity with orthogonal polarization, thereby easing the strong competition between this line and the relatively low-gain 9R, 9P and 10R branch lines within the gain medium which is common to both cavities.