Controlling Photon Transverse Orbital Angular Momentum in High Harmonic Generation

TL;DR

This paper explores how transverse optical orbital angular momentum can be controlled in high harmonic generation using spatiotemporal optical vortex pulses, revealing unique spectral structures and a method for topological charge control.

Contribution

It presents the first study on HHG with transverse orbital angular momentum driven by STOV pulses and introduces a robust control method for the harmonic spectral and topological properties.

Findings

Observation of unique spatio-spectral structures in harmonic spectra.

Identification of the origin of these structures from microscopic and macroscopic effects.

Demonstration of a method to control the topological charge of high-order harmonics.

Abstract

High harmonic generation (HHG) with longitudinal optical orbital angular momentum has attracted much attention over the past decade. Here, we present the first study on the HHG with transverse orbital angular momentum driven by the spatiotemporal optical vortex (STOV) pulses. We show that the produced spatial resolved harmonic spectra reveal unique structures, such as the spatially spectral tilt and the fine interference patterns. We show these spatio-spectral structures originate from both the macroscopic and microscopic effect of spatiotemporal optical singularity in HHG. Employing two-color counter-spin and counter-vorticity STOV pulses, we further discuss a robust method to control the spatiotemporal topological charge and spectral structure of high-order harmonics. The conservation rule of photon transverse orbital angular momentum in HHG process is also discussed when mixing with photon spin angular momenta.