In the paper, we applied the paraxial region theory and Wentzel–-Kramers–-Brillouin approximation to study laser beam self-focusing in the interaction of laser and collisional plasma with periodical density ripple. The results have shown that, under the influence of collision nonlinear effect, laser presents stable self-focusing, self-defocusing, and oscillational self-focusing in the plasma. Besides, the parameters of plasma with periodical density ripple have a greater impact on the effect of self-defocusing and oscillational self-focusing than stable self-focusing. In certain conditions, beam self-defocusing and oscillational self-focusing would decline and even disappear, and stable self-focusing would further be strengthened. Hence, selecting a suitable periodic plasma system is advantageous for separating self-defocusing and oscillational self-focusing, and for the formation of a more stable collisional self-focusing.

中文翻译：

---

具有周期性密度波动的碰撞等离子体中的激光束自聚焦

在本文中，我们应用近轴区域理论和Wentzel--Kramers--布里渊近似来研究激光与碰撞等离子体相互作用中具有周期性密度波动的激光束自聚焦。结果表明，在碰撞非线性效应的影响下，激光在等离子体中呈现稳定的自聚焦、自散焦和振荡自聚焦。此外，与稳定自聚焦相比，具有周期性密度波动的等离子体参数对自散焦和振荡自聚焦的影响更大。在一定条件下，光束自散焦和振荡自聚焦会下降甚至消失，稳定自聚焦会进一步加强。因此，