Time-resolved dynamics of two-dimensional transverse patterns in broad area lasers.

We report the first direct experimental observation of the fast dynamics (nanosecond scale) of complex two-dimensional transverse patterns in broad area lasers. The laser emission bright peaks forming the transverse patterns are observed to be aperiodically flashing in time with different growing rates. These optical filaments do not move along the cross section during their lifetime, which is close to 2 ns.

Time-resolved spatial profile of TEA CO2 laser pulses: influence of the gas mixture and intracavity apertures.

The evolution of the intensity profile of transversely excited atmospheric CO2 laser pulses is investigated within the intensity moment formalism. The beam quality factor M2 is used to study the mode evolution. Attention is focused on the influence of both the gas mixture (N2 :CO2 :He) and the diameter of an intracavity diaphragm placed to attenuate higher-order modes.

Complete spatial characterization of a pulsed doughnut-type beam by use of spherical optics and a cylindrical lens.

A complete spatial characterization (in second-order moments) of a doughnut-type beam from a pulsed transversely excited atmospheric CO2 laser is described. It includes the measurement of the orbital angular momentum carried by the beam. The key element in the characterization is the use of a cylindrical lens in addition to the usual spherical optics.

Time resolved pattern evolution in a large aperture laser.

We have measured quasiinstantaneous transverse patterns in a broad aperture laser. Nonordered patterns yielding to boundary determined regular structures in progressive time-integrated recording are observed. The linear analysis and numerical integration of the full Maxwell-Bloch equations allow us to interpret the features of the experiment.

Transverse pattern morphogenesis in a CO(2) 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 CO(2) laser. Transverse patterns are regular and repetitive in the long-pulse (1-micros 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.