Topology of Plasma Wakefields Driven by Two Color Laguerre Gaussian Laser Pulses

TL;DR

This paper analytically and numerically studies how two-color Laguerre Gaussian laser pulses with orbital angular momentum alter plasma wakefield structures, revealing new topologies and control mechanisms for plasma accelerators.

Contribution

It introduces a perturbative and quasi-cylindrical simulation framework to analyze the impact of structured laser modes on plasma wakefields, highlighting novel wakefield topologies and control options.

Findings

Finite azimuthal index reduces on-axis wakefields but redistributes energy radially.

Orbital angular momentum modes create hollow, ring-shaped wake structures.

Mixed Gaussian Laguerre modes combine features of both pure modes, enabling tailored wakefield control.

Abstract

Plasma wakefield excitation driven by two color Laguerre Gaussian laser pulses carrying orbital angular momentum is investigated analytically and through quasi-cylindrical particle in cell simulations. Using a perturbative framework together with the quasistatic approximation, the influence of the transverse laser mode structure on the longitudinal and transverse wakefields in an underdense plasma is examined in the weakly relativistic regime. The results show that drivers with finite azimuthal index produce reduced and less regular on-axis longitudinal wakefields compared to conventional Gaussian drivers. However, radial longitudinal field distributions reveal that this reduction originates from a redistribution of the wakefield energy toward finite radii rather than a simple loss of wake excitation. Orbital angular momentum carrying modes generate hollow and ring shaped wake structures accompanied by strongly modified transverse electric fields and broader plasma density perturbations. Mixed Gaussian Laguerre Gaussian configurations exhibit intermediate behavior, combining weak on-axis acceleration with pronounced off axis wake excitation. The study demonstrates that structured two-color laser drivers fundamentally modify the topology of plasma wakefields and provide an additional mechanism for controlling transverse plasma dynamics, off-axis acceleration, and angular momentum mediated wakefield structures in plasma based accelerator schemes.