Comparing Ray-Based and Wave-Based Models of Cross-Beam Energy Transfer

Ray-based models of cross-beam energy transfer (CBET) are used in radiation--hydrodynamics codes to calculate laser-energy deposition. The accuracy of ray-based CBET models is limited by assumptions about the polarization and phase of the interacting laser beams and by the use of a paraxial Wentzel--Kramers--Brillouin (WKB) approximation. A 3-D wave-based solver (\textit{LPSE}-CBET) is used to study the nonlinear interaction between overlapping laser beams in underdense plasma. A ray-based CBET model\footnote{I. V. Igumenshchev\textit{ et al.}, Phys. Plasmas \textbf{19}, 056314 (2012).} is compared to the wave-based model and shows good agreement in simple geometries where the assumptions of the ray-based model are satisfied. Near caustic surfaces, the assumptions of the ray-based model break down and the calculated energy transfer deviates from wave-based calculations. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.