Pattern control with spatial perturbations in a wide aperture laser

Pattern selection and stabilization by means of spatial perturbations is experimentally investigated in a wide aperture CO2 laser. Thin metallic wires are inserted into the laser cavity to realize the spatial perturbation. The effects of a single wire on the fundamental and annular patterns show that the diffraction induced by the wire plays an important role. By using more wires hexagons are obtained. By changing the cavity detuning we observed the transition from a hexagon to a dodecagon via the doubling of the azimuthal spatial frequency.