CO2 laser beam refraction in a linear discharge plasma

Beam guiding and focusing have been observed for CO2 laser propagation in a high-density low-temperature annular plasma. A TEA laser was fired along the axis of a cylindrical plasma column of densities in the 1016–1017-cm−3 range. Several radial density profiles were investigated. Beam guiding and focusing were observed when the density had a minimum on the axis. A density maximum on-axis refracted the beam toward the tube walls, and intense ``hot spots'' resulting from apparent filamentation inside the plasma were recorded.