Symmetry breaking in honeycomb photonic lattices

We study the phenomena associated with symmetry breaking in boneycomb photonic lattices. As the honeycomb structure is gradually deformed, conical diffraction around its diabolic points becomes elliptic and eventually no longer occurs. As the deformation is further increased, a gal) opens between the first two bands, and the lattice can support a gap soliton. The existence of the gal) soliton serves as a means to detect the symmetry breaking and provide an estimate of the size of the gap. (C) 2008 Optical Society of America