Phase-locked spatial domains and Bloch domain walls in type-II optical parametric oscillators - art. no. 056231

We study the role of transverse spatial degrees of freedom in the dynamics of signal-idler phase locked states in type-II optical parametric oscillato rs. Phase locking stems from signal-idler polarization coupling which arise s if the cavity birefringence and/or dichroism is not matched to the nonlin ear crystal birefringence. Spontaneous Bloch domain wall formation is obser ved numerically and the dynamics and chiral proper-ties of the fronts are i nvestigated. Bloch walls connect homogeneous regions of self-phase-locked s olutions by means of a polarization transformation. The parameter range for phase locking is found analytically. The polarization proper-ties and the dynamics of walls in one and two transverse spatial dimensions are explaine d. The transition from Bloch to Ising walls is characterized, the control p arameter being the linear coupling strength. The wall dynamics governs spat iotemporal dynamical states of the system, which include transient curvatur e driven domain growth, persistent dynamics dominated by spiraling defects for Bloch walls, and labyrinthine pattern formation for Ising walls.