Transverse orbital angular momentum of amplitude-perturbed fields

TL;DR

This paper experimentally measures the change in transverse orbital angular momentum of optical pulses caused by amplitude perturbations, confirming theoretical predictions and revealing how even Gaussian pulses with zero initial tOAM can acquire net tOAM.

Contribution

It provides the first experimental validation of the theory predicting tOAM changes due to amplitude perturbations in optical pulses.

Findings

Excellent agreement between measurements and simulations.

Amplitude perturbations can induce net tOAM in Gaussian pulses.

Clarification of theoretical approaches to tOAM analysis.

Abstract

We measure the change in transverse orbital angular momentum (tOAM) per photon, delta L_y, applied to an optical pulse by a pure amplitude perturbation. The results are in excellent agreement with calculations and simulations of the spatiotemporal torque based on our tOAM theory [Phys. Rev. Lett. 127, 193901 (2021)]. The crucial factor in determining delta L_y is the spatiotemporal distribution of tOAM density in the pulse. We show that even Gaussian pulses with zero total tOAM can have net tOAM induced by an amplitude perturbation stationary in the lab frame. As a prelude to the paper, we review and clarify several recent theoretical approaches to tOAM and reemphasize several fundamental principles needed for the correct analysis of experiments and simulations.