An experimental study has been carried out of the field distribution over the cross section of the 3.39 μ ASE beam from a helium-neon laser with a discharge tube 4 m long and 10 mm in diameter, operated far from saturation. It was found that the beam is channeled in the active medium of the laser and the result of this is that the beam diameter becomes much smaller than the tube diameter and, at the same time, the angular divergence of the beam approaches the diffraction limit.
Department of Optics
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