Bloch domain walls in type II optical parametric oscillators

Evidence of Bloch domain walls in nonlinear optical systems is given. These walls are found in the transverse fields of optical parametric oscillators when the polarization degree of freedom, the cavity birefringence, and (or ) dichroism are taken into account. These domain walls arise spontaneously and exhibit defects where Bloch walls of different chirality join together. Two dynamic regimes are found: In the first one the vector field approache s a final homogeneous state, and in the other the walls are continually gen erated and annihilated. This dynamic behavior is caused by the fact that wa lls of opposite chirality move spontaneously with opposite velocity. (C) 20 00 Optical Society of America.