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arXiv 2102.07939nlin.PSphysics.optics
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二次谐波产生晶格中的嵌入孤子

Embedded solitons in second-harmonic-generating lattices

Hadi Susanto, Boris A. Malomed

摘要:

嵌入孤子是非线性波系统中的一种特殊模式,其传播常数落在系统的传播带内。一个特别具有挑战性的课题是在非线性动力学晶格(离散系统)中寻找这样的模式。我们解决这个问题的耦合离散方程模型的光传播的隧道耦合波导的阵列与固有的二次(二次谐波产生)和立方非线性的组合系统。通过两种解析近似构造了离散嵌入孤子(DES)的解,并分别对宽DES和窄DES进行了调整,并借助于数值计算得到了系统的形式。产生了几种类型的DES,包括基频和二次谐波分量具有相同和相反符号的DES。在最相关的情况下,狭窄的DES,分析近似产生非常准确的结果,与数值结果相比。在这种情况下,DES分支从传输带延伸到半无限大的间隙作为一个家庭的规则离散孤子。对离散事件系统稳定性的研究表明,除了具有半稳定性的离散事件系统外,还存在线性稳定的离散事件系统,它们是真正的鲁棒模式。

英文摘要:

Embedded solitons are exceptional modes in nonlinear-wave systems with the propagation constant falling in the system's propagation band. An especially challenging topic is seeking for such modes in nonlinear dynamical lattices (discrete systems). We address this problem for a system of coupled discrete equations modeling the light propagation in an array of tunnel-coupled waveguides with a combination of intrinsic quadratic (second-harmonic-generating) and cubic nonlinearities. Solutions for discrete embedded solitons (DESs) are constructed by means of two analytical approximations, adjusted, severally, for broad and narrow DESs, and in a systematic form with the help of numerical calculations. DESs of several types, including ones with identical and opposite signs of their fundamental-frequency and second-harmonic components, are produced. In the most relevant case of narrow DESs, the analytical approximation produces very accurate results, in comparison with the numerical findings. In this case, the DES branch extends from the propagation band into a semi-infinite gap as a family of regular discrete solitons. The study of stability of DESs demonstrates that, in addition to ones featuring the well-known property of semi-stability, there are linearly stable DESs which are genuinely robust modes.

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