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Type of orbital angular momentum in γ-rays generated in laser–plasma interactions

Determine the type of orbital angular momentum (intrinsic versus extrinsic) carried by γ-ray photons generated in laser–plasma interactions when emission is modeled using semiclassical, incoherent modules, in order to assess the suitability of such γ-ray beams for nuclear physics experiments that require well-defined intrinsic OAM.

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Background

The paper reviews theoretical proposals and simulations for producing high-energy photons with orbital angular momentum (OAM), including schemes based on inverse Compton/Thomson scattering with vortex laser pulses and direct laser–plasma interactions. While semiclassical radiation modules are widely used in simulations to model γ-ray emission, they treat the process as incoherent, which may affect the nature of the resulting photon OAM.

The authors explicitly flag an unresolved issue: whether the γ-ray photons produced in these scenarios carry intrinsic OAM (suitable for nuclear physics applications requiring well-defined angular momentum transfer) or extrinsic OAM (which may be unsuitable). They call for new experiments and improved modeling to clarify this fundamental point.

References

The generation of OAM carrying γ-rays is a promising, but a relatively new area of research. As such it has a number of open questions. In simulations, the γ-ray emission is modeled using semiclassical modules that treat the process as incoherent. However, it raises a question regarding the type of OAM that is being carried by the emitted photons (e.g., see Ref. for a discussion of different types of OAM). The concern is that the γ-rays bearing extrinsic OAM may not be suitable for nuclear physics experiments.

— Advances in laser-plasma interactions using intense vortex laser beams (2405.17852 - Shi et al., 28 May 2024) in Section 3.4, Generation of X-rays and γ-rays carrying OAM