Manipulation of Superposed Vortex States of γ Photon via Nonlinear Compton Scattering

Vortex γ photons in superposition states have important applications in photonuclear, high-energy, and strong-field physics. However, their controlled generation in the γ-ray regime remains a great challenge. Here, we put forward a novel method for the generation of vortex γ photon in superposition states, with controllable orbital angular momentum (OAM) separation Δell^prime and modal weights, via nonlinear Compton scattering driven by multifrequency circularly polarized laser fields. We develop a strong-field quantum electrodynamics (QED) framework to reveal the underlying mechanism and calculate the radiation probabilities. In our method, the superposition arises from interference between energy-degenerate multiphoton pathways carrying distinct OAM. For two-frequency fields, the OAM separation follows Δell'=νmp1 (upper/lower sign for equal/opposite helicities), and modal weights are tunable by laser intensities, with ν the frequency ratio. Vortex γ photons in controllable superposition states from our method have significant applications in strong-field QED and nuclear photonics.