Transverse pattern morphogenesis in a CO2 laser

Irregular and nonrepetitive transverse intensity distributions were measured in the near field during the gain-switch pulse (60-ns width) of a transversely excited atmospheric CO2 laser. Transverse patterns are regular and repetitive in the long-pulse (1-mu s width) mode and in ensemble average in the short-pulse mode, and in both cases symmetry is imposed by the boundary conditions. Short-pulse transverse patterns formed by lasing domains appear with a mean size of 0.8 mm. The prediction of domain size based on a model of population inversion filamentation agrees with the experimental result. (C) 1996 Optical Society of America