Some characteristics of near-infrared He–Ne laser radiation

Stimulated emission was obtained from a small (resonator length ~0.5 m) prototype He–Ne laser emitting simultaneously at wavelengths of 1.0798, 1.1614, and 1.1985 μ (common upper level 2S₂), at 1.0844, 1.1523, and 1.1767 μ (common upper level 2S₂), and at 3.3913 μ with an upper level 3S₂. Competition between the transitions coupled by common energy levels was observed. The output power of each of the competing transitions varied periodically and the period was Δ L = λ₁λ₂/2(λ₁ – λ₂). Waveguide emission at wavelengths of 1.15 and 3.39 μ was observed in a resonator with large diffraction losses.