MODULATIONAL INSTABILITY AND PATTERN-FORMATION IN THE FIELD OF NONCOLLINEAR PUMP BEAMS

We study pattern formation that is due to modulational instability of noncollinear counterpropagating beams. Angular misalignment of the pum ps over a broad range leads to the generation of lines oriented perpen dicular to the plane of the pump beams. A theoretical expression for t he angular separation of the lines is in close agreement with observat ions. Outside this range, for both small and large misalignments, we o bserve squeezed hexagonal patterns. (C) 1997 Optical Society of Americ a.