Intense high-harmonic optical vortices generated from a micro-plasma-waveguide irradiated by a circularly polarized laser pulse

TL;DR

This paper proposes a novel method to generate intense high-harmonic optical vortices using a circularly polarized laser in a micro-plasma-waveguide, demonstrating efficient harmonic conversion through nonlinear plasma interactions.

Contribution

It introduces a new scheme leveraging spin-orbit interaction in a micro-plasma-waveguide to produce high-order harmonic optical vortices with high efficiency.

Findings

Achieves approximately 5% harmonic conversion efficiency.

Demonstrates phase velocity matching of harmonics to the driving laser.

Shows nonlinear plasma response modifies electromagnetic modes at high intensities.

Abstract

A scheme for generating intense high-harmonic optical vortices is proposed. It relies on spin-orbit interaction of light when a relativistically-strong circularly polarized laser pulse irradiates a micro-plasma-waveguide. The intense laser field drives a strong surface wave at the inner boundary of the waveguide, which leads to high-order harmonic generation as the laser traveling inside. For a circularly polarized drive laser, the optical chirality is imprinted to the surface wave, which facilitates conversion of spin angular momentum of the fundamental light into orbital angular momenta of the harmonics. A "shaken waveguide" model is developed showing that the aforementioned phenomena arises due to nonlinear plasma response that modifies electromagnetic mode at high intensities. We further show the phase velocities of all the harmonic beams are automatically matched to the driving laser, so that the harmonic intensities increase with propagation distance. The efficiency of harmonic production are related to the surface wave breaking effect, which can be significantly enhanced using a tightly focused laser. Our simulation suggests an overall conversion efficiency $\sim5\%$ can be achieved.