F-函数扩展法求解超介质中的亮孤子和暗孤子

利用F-函数扩展法求解超介质中的超短脉冲传输方程, 探讨了超介质中的反常自陡效应和特有的二阶非线性色散效应所导致的新的孤子现象和规律. 结果表明, 正折射区的二阶非线性色散效应可以代替线性色散效应形成亮孤子; 正、负折射区的反常自陡效应由于其符号可改变, 从而可在特定条件下分别在反常色散和正常色散区形成有别于常规介质的亮、暗孤子; 反常自陡效应的符号或者反常自陡效应和三阶线性色散效应的相互比较关系能够控制亮、暗孤子中心的漂移方向.关键词：孤子超介质F-函数扩展法

Bright and dark solitons in metamaterials obtained by extended F-expansion method

The ultra-short pulse equation in a metamaterial is solved by the extended F-expansion method. The new phenomena and characteristics of solitons, caused by the anomalous self-steepening effect and the second-order nonlinear dispersion in metamaterials, are discussed. The results show that the second-order nonlinear dispersion in the positive-index region may take the place of the linear dispersion to form the bright and dark solitons. Due to the switchable sign of the anomalous self-steepening effect in the positive-index and negative-index regions, the bright and dark solitons separately exist in the anomalous and normal dispersion regions under some specific conditions. The moving directions of the centers of bright and dark solitons can be controlled by the sign of the anomalous self-steepening effect or by the combination of the anomalous self-steepening effect and third-order linear dispersion.