Time averaging of irregular spatiotemporal patterns of a large aperture laser in transitory regime

By means of a new experimental technique, we measure quasi-intantaneous tra nsverse intensity patterns in the gain-switch peak of a transversely excite d atmospheric CO2 laser with large aperture. The patterns recorded with a 2 ns resolution show a completely irregular spatiotemporal behavior, but whe n the exposure time of the measurements increases, boundary-determined orde red structures can be observed. As a quantification of this averaging proce ss, the contrast of the intensity distributions decreases as the time integ ration grows. The results are numerically reproduced by integration of the full Maxwell-Bloch equations.