  We demonstrate experimentally how semiconductor lasers subjected to double
optical feedback change the statistics of their chaotic spiking dynamics from
Gaussian to long-tail Power Law distributions associated to the emergency of
bursting. These chaotic regimes, which are features of excitable complex
systems, are quantified by the tail exponent $\alpha$ and appear by changing
the ratio between the feedback times. Transitions to bursting occur in the
neighbourhood of low order Farey fractions. The physics behind these
transitions is related to the variation of threshold pump current in the
compound system as obtained from a deterministic set of rate equations.
Numerical integration also verifies the observed chaos transitions indicating
the possibility of controlling the bursting chaotic statistics.
