In many-cycle plane waves at intermediate intensities, the nonlinear trident process can be well approximated by the two sequential steps of nonlinear Compton scattering of a polarized real photon followed by its transformation into an electron-positron pair via nonlinear Breit-Wheeler pair creation. We investigate this two-step process in the intermediate intensity regime by employing the locally monochromatic approximation for each step and numerically evaluating resulting expressions. When photon polarization is included, it is found to produce an order 10% decrease in the trident rate: the importance of polarization increases at lower intensities, and decreases at higher intensities. Its importance persists at higher intensities in a linearly polarized background, but disappears at high intensities in a circularly polarized background. If the two steps are made to take place in two linearly polarized plane wave pulses with perpendicular polarizations, the pair yield can be increased by approximately 30% compared to two plane waves with the same polarization. It is also shown that harmonic structures in the Compton step can be passed to the pair step if the Compton edge is at an energy of the order of the threshold for linear Breit-Wheeler.

• Received 2 December 2022
• Accepted 18 April 2023

DOI:https://doi.org/10.1103/PhysRevD.107.096004

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Published by the American Physical Society