Conservation and non-conservation of photonic angular momentum in a gradient-index fiber

Photonic angular momentum (AM), including the orbital AM (OAM) and spin AM (SAM) of vector vortex beams (VVBs) and partially-coherent VVBs, is analyzed in gradient-index (GRIN) fiber transmission. Photonic spin-orbit interactions (SOIs) occur and the photonic SAM, OAM, and AM (the sum of SAM and OAM) of radially-polarized vortex beams (RVBs) and partially-coherent RVBs (PRVBs) on different planes in the GRIN fiber are simulated. The photonic AM is conserved or not conserved from the SOIs of the RVB and PRVB during GRIN fiber trans-mission. Simultaneously, the non-conservation characteristics of the photonic AM are regulated by coherence.