Growth, saturation, and collapse of laser-driven plasma density gratings

The plasma density grating induced by intersecting intense laser pulses can be utilized as optical compressors, polarizers, waveplates, and photonic crystals for the manipulation of ultra-high-power laser pulses. However, the formation and evolution of plasma density grating are still not fully understood as linear models are adopted to describe them usually. In this paper, two theoretical models are presented to study the formation process of plasma density grating in the nonlinear stages. In the first model, an implicit analytical solution based on the fluid equations is presented, while in the second model, a particle-mesh method is adopted. It is found that both models can describe the plasma density grating formation at different stages, well beyond the linear growth stage. More importantly, the second model can reproduce the phenomenon of ion “wave-breaking” of plasma density grating, which eventually induces the saturation and collapse of plasma density grating. Using the second model, the saturation time and maximum achievable peak density of plasma density grating are obtained as functions of laser intensity and plasma density, which can be applied to estimate the lifetime and capability of plasma density grating in experiments. The results from these two newly developed models are verified using particle-in-cell simulations.