Ultraviolet lasing in helium-nitrogren mixtures

The influence of helium admixtures on ultraviolet lasing (337.1 nm) in a coaxial nitrogen laser is investigated experimentally. The addition of helium expands the region of pressures within which lasing exists, but the lasing intensity drops off. An experimental setup incorporating a glass discharge tube 48.5 cm long and 0.4 cm in diameter is described. Lasing in coaxial lasers is found to be determined basically by the dynamics and parameters of the breakdown waves, regardless of the composition of the gas. The addition of helium makes it possible to increase the overall working pressure of the gas in a nitrogen laser without reducing the peak power of the laser significantly. The laser pulse length is shorter in helium-nitrogen mixtures than in pure nitrogen. The length of the tube must be increased or decreased correspondingly in order to obtain the first or second laser peak for a given pressure.