Second harmonic generation of spatiotemporal optical vortices and conservation of orbital angular momentum

TL;DR

This paper demonstrates the first experimental and theoretical generation of second harmonic of spatiotemporal optical vortices, confirming the conservation of their unique orbital angular momentum orthogonal to propagation, revealing new properties of light.

Contribution

It introduces the first demonstration of second harmonic generation in STOVs and confirms the conservation of their orthogonal orbital angular momentum.

Findings

Successful generation of second harmonic STOVs.

Verification of OAM conservation in the process.

Evidence that photons can have intrinsic OAM perpendicular to propagation.

Abstract

Spatiotemporal optical vortices (STOVs) are a new type of intrinsic optical orbital angular momentum (OAM) structure in which the OAM vector is orthogonal to the propagation direction [Optica 6, 1547, (2019)] and the optical phase circulates in space-time. Here, we experimentally and theoretically demonstrate, for the first time, the generation of the second harmonic of a STOV-carrying pulse along with the conservation of STOV-based OAM. Our experiments verify that individual photons can have intrinsic orbital angular momentum perpendicular to their propagation direction.