Orbital Angular Momentum in Noncollinear Second Harmonic Generation by off-axis vortex beams

TL;DR

This paper experimentally investigates how orbital angular momentum behaves in noncollinear second harmonic generation using off-axis vortex beams, revealing that the SH signal always carries zero angular momentum despite input beam displacements.

Contribution

It demonstrates the behavior of fractional orbital angular momentum in noncollinear SHG with off-axis vortex beams, providing new insights into OAM transfer in nonlinear optics.

Findings

SH signal always has zero angular momentum despite input beam displacement

Different spatial configurations of SH field observed under phase matching

Fractional OAM beams used as input in noncollinear SHG

Abstract

We experimentally study the behavior of orbital angular momentum (OAM) of light in a noncollinear second harmonic generation (SHG) process. The experiment is performed by using a type I BBO crystal under phase matching conditions with femtosecond pumping fields at 830 nm. Two specular off-axis vortex beams carrying fractional orbital angular momentum at the fundamental frequency (FF) are used. We analyze the behavior of the OAM of the SH signal when the optical vortex of each input field at the FF is displaced from the beam's axis. We obtain different spatial configurations of the SH field, always carrying the same zero angular momentum.