Moving Bragg Grating Solitons in a Grating-assisted Coupler with Cubic-Quintic Nonlinearity

摘要

We analyze the existence of moving Bragg grating solitons in a semilinear coupled system where one core is equipped with a Bragg grating and has cubic-quintic nonlinearity and the other is linear. The system's linear spectrum contains three bandgaps, namely the upper, lower and central gaps. The bandgap edges shift with the soliton velocity (s) and group velocity mismatch term (c) for a given coupling coefficient (κ), and result in change in the spectral widths. Two families of moving Bragg grating solitons (referred to as Type 1 and Type 2) are found that fill the upper and lower gaps only. No moving solitons are found in the central gap. The border separating the two families depends on both c and s, and is determined numerically. We carried out systematic numerical stability analysis of the moving solitons and identified non-trivial stability borders in their parametric plane. The analysis also reveals that vast areas of stable Type 1 solitons exist in the system's parametric plane and that all Type 2 solitons are unstable.