A new class of stable composite soliton in two-dimensional photonic lattice

We demonstrate that a new class of stable composite soliton exists in a two-dimensional lattice. It can be produced by the evolution of a stationary solution of nonlinear Schrdinger equation with a periodic potential modulation. We emphasize that this new kind of composite soliton is different from the dipole soliton reported before though they seem alike. The components of the soliton exchange energy during the propagations and the total energy of soliton conserves.