Measurement of the formation and evolution of a strange attractor in a laser

The fractal dimensions and Kolmogorov entropies of periodic and chaotic attractors for a CO2 laser system with modulated losses are measured. In particular, an increase in dimension is found near the accumulation point of the periodic cascade according to the Feigenbaum scaling law, besides the expected usual increase of the attractor dimension in the chaotic region. Numerical solutions of a theoretical model yield dimensions in quantitative agreement with the experiments, thus demonstrating a close match of experiment and theory for this physical system.