随着飞秒脉冲成丝在诸多领域中的广泛应用,延长成丝距离和伴随的等离子体通道长度成为应用的关键。通过求解广义非线性薛定谔方程以及电子密度演化方程,得出如果采用同能量的叠加高斯光束而不采用普通单一高斯光束作为入射光束,克尔介质中飞秒成丝和等离子体通道的性能会显著提高。根据自聚焦上限阈值功率的理论计算表明,叠加高斯光束的自聚焦上限阈值功率大于普通高斯光束。因此,采用叠加高斯光束作为入射光束,既可以延长成丝距离,又能避免高能脉冲下多丝的存在。

Femtosecond pulse filamentation has wide applications in many fields. Extending the lengths of filamentation and accompanied plasma channel are the key to application. By solving the extended nonlinear Schr dinger equation coupled with the electron density equation, we can get the following conclusion that the performance of femtosecond filamentation and plasma channels in Kerr media can be significantly improved if an superposed Gaussian beam with the same energy is used instead of an ordinary single Gaussian beam as the incident beam. According to theoretical calculation of the upper threshold power for self-focusing, the self-focusing upper threshold power of superposition Gaussian beam is larger than that of single Gaussian beam. Hence, superposed Gaussian beam as incident beam is particularly useful to extend the filament length and avoid multi-filamentation when the incident pulse energy is high.