The sub-relativistic laser beam interaction with an underdense plasma is investigated via two-dimensional (2D) numerical simulations with respect to the laser polarization direction. Different parametric instabilities dominate the interaction depending on the propagation direction of the daughter waves in the simulation plane with respect to the laser field polarization and laser propagation direction. In the plane containing the laser electric field (p-polarization) the interaction is dominated by the two-plasmon decay instability and the beating of large amplitude electron plasma waves produces periodic ion density perturbations suppressing stimulated Raman scattering in the quarter critical density zone. A stronger absorption and heating of hot electrons is observed in the case where laser polarization is perpendicular to the simulation plane (s-polarization). Furthermore, by comparing a plane laser wave with a narrow beamlet, the effect of the initial transverse laser profile is proven to play an important role in exciting the filamentation instability, which competes with stimulated Brillouin scattering and affects the laser absorption and hot electron generation. A dedicated three-dimensional simulation indicates that a 2D simulation with p-polarization produces a more reliable results while the case of s-polarization overestimates the laser absorption and hot electron generation.

通过关于激光偏振方向的二维 (2D) 数值模拟研究亚相对论激光束与低密度等离子体的相互作用。取决于子波在模拟平面中相对于激光场偏振和激光传播方向的传播方向，不同的参数不稳定性在相互作用中占主导地位。在包含激光电场（p 极化）的平面中，相互作用由双等离子体衰变不稳定性主导，并且大振幅电子等离子体波的跳动产生周期性离子密度扰动，抑制了四分之一临界密度区中的受激拉曼散射。在激光偏振垂直于模拟平面（s 偏振）的情况下，观察到热电子的吸收和加热更强。此外，通过将平面激光波与窄子束进行比较，证明初始横向激光轮廓的影响在激发丝状不稳定性方面起着重要作用，它与受激布里渊散射竞争并影响激光吸收和热电子产生。专用的 3D 模拟表明 p 偏振的 2D 模拟产生更可靠的结果，而 s 偏振的情况高估了激光吸收和热电子的产生。初始横向激光轮廓的影响被证明在激发丝状不稳定方面起着重要作用，它与受激布里渊散射竞争并影响激光吸收和热电子的产生。专用的 3D 模拟表明 p 偏振的 2D 模拟产生更可靠的结果，而 s 偏振的情况高估了激光吸收和热电子的产生。初始横向激光轮廓的影响被证明在激发丝状不稳定方面起着重要作用，它与受激布里渊散射竞争并影响激光吸收和热电子的产生。专用的 3D 模拟表明 p 极化的 2D 模拟产生更可靠的结果，而 s 极化的情况高估了激光吸收和热电子的产生。