Biconical emission of spatially mode-locked patterns with wave-number ratio √2 in a ring cavity device

Biconical emission with wave-number ratio {}2 is observed in the numerical simulations of the ring cavity with diffraction effects, on the defocusing side of the resonance. As the intensity of the plane-wave input beam increases, a sequence of stationary patterns is observed, and understood via a nonlinear analysis. The first pattern with (4-4) peaks is a bisquare resulting from a strong coupling between two quasiresonant sets of modes with wave numbers K and {}2K. This pattern destabilizes at the onset of the drift bifurcation, into a new (4-4) pattern with a smaller wavelength, that splits into two twisted bisquares, with a 53^∘{} rotation angle ensuring the wave-vector locking, or the spatial periodicity of this (8-8) structure. {} 1996 The American Physical Society.