Sequential formation of multiple lattice gap solitons in defocusing photovoltaic–photorefractive crystals

• Sequential formation of MGSs in defocusing PP crystals is reported.
• The lobes of MGSs are the same intensity except for the side lobes.
• The small intensity of the side lobes increases with the propagation constant.
• The existence domain of MGSs decreases with decreasing the lattice depth.
• MGSs do not exist when the lattice depth equals a certain threshold value.

We show that an odd- or even-numbered sequence of multiple gap solitons (MGSs) supported by optical lattices imprinted in defocusing photovoltaic–photorefractive (PP) crystals is possible. The side lobes of MGSs are the small intensity, which can be controlled by changing the propagation constant. The lobes of MGSs are the same intensity except for the side lobes. The existence domain of MGSs decreases with decreasing the lattice depth and vanishes when the lattice depth decreases to below a certain threshold. The stability of MGSs has been investigated numerically and it has been found that they are stable.