Investigation of laser absorption efficiency in planar plasma produced by laser irradiation at various incidence angles

Laser absorption in plasma plays a critical role in energy coupling and symmetry driving in laser direct-drive implosions, particularly in polar direct drive. The incidence angle of the laser significantly influences absorption efficiency. In this paper, the absorption of a 351 nm laser in planar CH plasma at oblique incidence is numerically simulated using the one-dimensional radiation-hydrodynamic code MULTI. Scaling laws of total absorption efficiency with varying laser incidence angles and intensities are obtained. The analytical model for laser time-dependent absorption [B. Scheiner and M. Schmitt, Phys. Plasmas 26(2), 024502 (2019)] is modified with the simulation results. Furthermore, a novel design incorporating a prepulse is proposed to enhance laser absorption. These results provide insights into optimizing the design of future polar direct-drive experiments.