Nonlocal Orbital-Angular-Momentum Dichroism of Vortex Light in Strained Crystals

Vortex light carries orbital angular momentum (OAM) in its transverse phase. We show that the transverse phase cannot generate OAM-odd absorption in any continuously translation-invariant system, even when optical nonlocality and multipole light–matter coupling are included. The combination of broken continuous translation symmetry and finite-range optical nonlocality permits OAM dichroism through transverse-momentum mixing; in nonuniformly strained Dirac materials, the dichroism factorizes into a nonlocal elasto-optic tensor and the overlap of the strain texture with the vortex transverse phase current.