Laser Operation at 339 μ in a Helium–Neon Mixture

Laser oscillation has been observed at 3.39 μ in a helium–neon mixture excited by a rf discharge. The transition is shown to be 3s2 → 3p4 in neon. It corresponds to the originally observed transition 2s2 → 2p4 at 11,523 Å and the more recently observed visible transition 3s2 → 2p4 at 6328 Å. Lasers have also been observed oscillating simultaneously on the visible and the 3.39 μ lines. In such cases the power output in the visible is reduced, and the infrared imposes its own mode structure upon the visible output from a confocal resonator.