Spin-orbit interactions in a nonlinear medium due to a nonlinear-induced geometric phase

In general, a spin-polarized light beam cannot couple its spin angular momentum (SAM) with intrinsic orbital angular momentum (IOAM) without spin reversal. Here we find that nonlinear media can give the spin-polarized photon an IOAM, as they travel in the media due to the nonlinear susceptibility along the transmission direction, which does not require spin reversal. To characterize this SAM-to-IOAM conversion process, we establish an evolution ray equation for photons carrying IOAM by reference to the Schrodinger equation. We further reveal the inherent physics of such a phenomenon from a full-wave perspective and find that the vortex generation originates from the nonlinear-induced geometric phase. (C) 2021 Optical Society of America

Automated summary

In general, a spin-polarized light beam cannot couple its spin angular momentum (SAM) with intrinsic orbital angular momentum (IOAM) without spin reversal. However, it has been found that nonlinear media can give the spin-polarized photon an IOAM without requiring spin reversal. This phenomenon is characterized by an evolution ray equation for photons carrying IOAM, and the vortex generation is shown to originate from the nonlinear-induced geometric phase.