GAIN MEASUREMENTS AT 543 NM IN HELIUM-NEON LASER DISCHARGES

A single-mode frequency stable helium neon laser operating on the 543 nm neon transition was used to probe an electrical discharge in helium neon mixtures. Values for the optical gain at this wavelength were ob tained. A comparison with the widely documented behaviour of the 633 n m transition, which shares the same upper state as the 543 nm transiti on, shows a marked difference in the variation of the optical gain wit h discharge pressure. This is shown to occur due to the differing beha viour of the lower laser state population densities with pressure. It is proposed that this could be due to the resonance peak in the electr on excitation cross section from the ground state to the 2P(10) level. Variation of gain with discharge current is also presented.