Relativistic Oscillating Window Driven by an Intense Laguerre Gaussian Laser Pulse

TL;DR

This paper investigates high-order harmonic generation using intense Laguerre-Gaussian laser pulses, revealing complex angular momentum interactions and predicting the resulting harmonic modes and their properties through theory and simulations.

Contribution

It introduces a new theoretical framework for predicting harmonic topological charges and intensities in LG-driven high-order harmonic generation, considering polarization effects.

Findings

Multiple LG modes are generated at each harmonic order.

The number of modes equals the harmonic order.

The theory accurately predicts mode charges and intensities.

Abstract

High-order harmonic generation by the diffraction of an intense Laguerre-Gaussian (LG) laser beam through a small aperture is studied. It is found that the 2D peripheral electron dynamics on the rim can facilitate complex interplay between the spin and orbital angular momentum interaction, which leads to distinct selection rules for LG pulses with different polarization states. In particular, when the driver is linearly polarized, the harmonic beams no longer follow a simple orbital angular momentum conservation rule. Instead, multiple LG modes with different topological charges are produced in each harmonic beam, and the number of modes equals to the harmonic order. A theory is derived and validated by simulations, which can predict the harmonic topological charges as well as their relative intensities for LG drivers with different polarization states. Our work provides fundamental insight into the behavior of light in nonlinear optics, and paves the way towards high-intensity UV or X-ray pulses carrying controllable OAM, that can serve as versatile tools at frontiers of various scientific fields.