Abstract
The interaction of two parallel relativistic laser beams in underdense plasmas is investigated by considering the evolution of their wave envelopes. The energy transfer between the two lasers is given by an expression based on the evolution of the total laser power in a regime without beam mixing. It is shown that how the energy is transferred depends nonlinearly on the initial phase difference of the lasers, and the result of the interaction depends on the laser intensity, spot radius, and their separation distance. The results are verified by direct numerical solution of the relativistic nonlinear Schrödinger equations for the laser envelopes as well as particle-in-cell simulation. The study and results should be helpful for understanding the energy transfer behavior of multiple co-propagating laser beams in underdense plasmas.
Highlights
Intense laser–plasma interactions (LPIs) have attracted much research attention because of their relevance to inertial confinement fusion (ICF),1 laser-driven table-top particle acceleration,2–4 etc.5 The ponderomotive force of an intense laser beam can expel the affected plasma electrons, leading to self-focusing and selfchanneling, as well as filamentation of the laser6,7 in underdense plasmas
It is shown that how the energy is transferred depends nonlinearly on the initial phase difference of the lasers, and the result of the interaction depends on the laser intensity, spot radius, and their separation distance
The study and results should be helpful for understanding the energy transfer behavior of multiple co-propagating laser beams in underdense plasmas
Summary
Intense laser–plasma interactions (LPIs) have attracted much research attention because of their relevance to inertial confinement fusion (ICF), laser-driven table-top particle acceleration, etc. The ponderomotive force of an intense laser beam can expel the affected plasma electrons, leading to self-focusing and selfchanneling, as well as filamentation of the laser in underdense plasmas. It was noted that the previous case was mainly concentrated on the interaction behavior at the nonlinear stage for a long propagation distance, where the two laser beams are already strongly dissipated and mixed up due to the nonlinear response of plasma. This makes it difficult to calculate the ratio of energy transfer between the lasers. A relatively simple expression for the evolution of the total laser power in the half space is obtained It describes how the energy is transferred in an initial interaction stage for a short propagation distance, where the laser energy is not seriously dissipated and the two beams are self-trapped without mixing up. The dependencies on the intensities, spot sizes, and separation distance of the lasers are obtained, and the results are found to agree well with those obtained by numerically solving the NSEs as well as by direct PIC simulation
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