Speckle experiments in random lasers

We present measurements of speckle in a random laser. We analyze its first-order statistics and show that,
contrary to what might be expected for passive systems, analyses of the intensity distribution P(I) and the
speckle spot size do provide information about light transport inside the system. P(I) is used to determine the
degree to which an incident probe is amplified by the random laser. The shrinking speckle spot size reflects the
change in path length distribution P(Λ) we deduce that the average path length (Λ) in the studied random
laser is two times longer above threshold than in a passive diffusive system.