Noise- and dynamics-sustained patterns in a nonlinear photorefractive system

We analyze experimentally the dynamics of optical patterns emerging from a photorefractive two-wave mixing geometry where a tilted single-feedback mirror generates an advectionlike effect. Depending on the nonlocal coupling (introduced by the tilting angle) between the two counterpropagating beams, the strength of the nonlocal response of the nonlinear photorefractive bulk medium, and the distance between the mirror and the crystal, we observe the initiation of different pattern geometries, the inversion of pattern transverse phase velocity, and the bifurcation from convective to absolute instabilities.