  We experimentally investigate the interplay between spatial shock waves and
the degree of disorder during nonlinear optical propagation in a thermal
defocusing medium. We characterize the way the shock point is affected by the
amount of disorder and scales with wave amplitude. Evidence for the existence
of a phase diagram in terms of nonlinearity and amount of randomness is
reported. The results are in quantitative agreement with a theoretical approach
based on the hydrodynamic approximation.

Optics