This paper reports the measurements for the axial mode competition in the 636.0 nm He-Cd II laser at several He pressures. The beginning conditions for the actual mode competition are examined experimentally, and discussed qualitatively from the viewpoints of the broadening mechanisms of the spectral lines. As a result, the axial mode separation at the beginning point of the mode competition gives the upper laser level decay rate γa under the actual lasing condition at 636.0 nm Cd II line. Based on experiments, the upper and lower laser level decay rates γa and γb, and hence the γab (mean value of γa and γb), are all determined along with the collision cross sections of the excited lasing state Cd atoms with buffer gas (He) atoms. The derived values of γa (0)49.5 MHz at the zero-pressure limit, which yields the radiative life time of the upper laser level at 3.2 ns, and the collision corss section σHe1.710-16 cm2 are roughly consistent with those reported based on the theoretical calculations. The experimentally determined He pressure dependence of the γa is expressed by γa49.51PHe(MHz), where PHe is the He pressure. For example, at PHe6 Torr, γa56.5 MHz, γb121 MHz, and then γab(γaγb)/288.8 MHz.

Improvement of the frequency stability in a 3.39 µm He-Ne laser in which the hump profile of the magnetic modulation signal (MMS) is used as a control signal is performed by introducing an enriched isotope into the laser tube.