In this talk, we present results of theoretical studies and particle-in-cell (PIC) simulations of the interaction of high-power laser radiation with intensities up the presently potentially available limit of 10²³–10²⁴W/cm² with dense plasmas of various geometry configurations. We consider the situation when the laser pulse carries significant spin or orbital angular momentum having polarization close to circular of being spatially structured. The aim is to analyze mechanisms of the angular momentum transfer from electromagnetic fields to plasma in various interaction regimes and to identify conditions and laser and plasma parameters optimal for experimental verification of these mechanisms. We consider three families of interaction scenarios, which relate to (a) extremely strong laser pulses of multi-petawatt (PW) power; (b) strong PW and sub-PW pulses; and (c) laser fields of moderate intensity at the border between the non-relativistic and relativistic domains.

Firstly, we consider the Inverse Faraday Effect (IFE) induced by the radiation reaction force [1] in the interaction of extremely intense (~10²³W/cm² ) circularly polarized laser pulses with overdense plasma. We examine a multi-beam realization of the IFE looking at the possibility to demonstrate radiation-dominated plasma dynamics at laser powers ~10PW close to achieve with the modern laser facilities. For a four-beam interaction scheme, employing pulses with mutually close-to-orthogonal linear polarizations this power is shown sufficient for the excitation of a strong quasi static magnetic field through the IFE induced by radiation friction. We also discuss the role of quantum effects in radiation of high-energy photons and in electron dynamics. Quantum recoil  may appear significant at such laser intensities leading to a sizable suppression of the quasi-static magnetic field, which still however remains detectable.

Secondly, we address the angular momentum transfer from the laser field to plasma at lower intensities ~10²¹–10²²W/cm² due to effects of the plasma target geometry. We demonstrate strong absorption of the field angular momentum during propagation of a circularly polarized laser pulse through a cylindric cavity in an overdense plasma, within a setup similar to that recently considered by Jiang with coauthors [3]. We demonstrate the mechanism of angular momentum transfer resulting from the motion of electrons in a highly inhomogeneous electromagnetic field near the plasma surface, similarly to the vacuum heating mechanism of laser energy absorption near a sharp plasma boundary [4]. This setup also demonstrates the effect of a strong quasi-static magnetic field excitation with amplitudes up to 10GGs for the pump laser intensity ~10²²W/cm². Applying PIC simulations, we reveal  complex plasma dynamics which leads to a rather unexpected distribution of the transferred angular momentum inside the cylindric plasma target followed by the formation of a plasma pinch with strong azimuthal currents. We sketch this evolution analytically on the level of a simple qualitative model.

Finally, we consider orbital angular momentum transfer to diluted plasma in the field of structured light. We model such transfer from a Laguerre-Gaussian beam of moderate intensity <10¹⁸W/cm²  to free electrons. In correlation with the case (b) of the geometric mechanism, we observe that the electrons gain, in average, an angular momentum of the sign opposite to that of the beam, resulting in some «negative» angular momentum transfer. To explain the effect qualitatively, we develop a theoretical model based on a high-order perturbative approach to the description of electron motion in the field of a Laguerre-Gaussian beam. Our theory predictions are examined by numerical simulations for several electromagnetic field configurations.

References

[1] T. V. Liseykina, S. V. Popruzhenko, and A. Macchi, New Journal of Physics 18, 072001 (2016). 
[2] T. V. Liseykina, E.E. Peganov, S. V. Popruzhenko, Physical Review E, submitted.
[3] K. Jiang, A. Pukhov and C.T. Zhou, New Journal of Physics 23, 063054 (2021).
[4] F. Brunel, Physical Review Letters 59, 52 (1987).
[5] E. Dmitriev, Ph. Kornes, Phys. Rev. A 110, 013514 (2024).