Optical soliton formation and dynamic characteristics in photonic Moiré lattices

The effect of nonlinearity on the topologically protected linear interface modes in photonic moiré lattice is theoretically investigated. The linear topological mode of moiré lattice is transformed into a set of topological gap solitons under the focusing nonlinearity. These solitons are stable up to a certain propagation constant in the lattice range. Stable symmetric and antisymmetric dipole solitons as well as quadrupole solitons can be formed in the continuously-periodic photon moiré lattice, however, they exhibit only low amplitudes, which indicates weak nonlinearities even when the band gap of the moiré lattice is wide. In addition, the propagation dynamics of metastable and unstable quadrupoles are discussed. Therefore, if the initial beam has a high amplitude, it will either evolve into an unstable soliton that is not a member of the topological gap soliton family, or delocalization.