Topological dichroism and birefringence of twisted light

Material anisotropy produces differential absorption and birefringence of linearly polarized light; material chirality leads to differential absorption and birefringence of circularly polarized light. Here we highlight how anisotropic media can produce a differential absorption and birefringence which depends on the sign of the topological charge ℓ of a focused optical vortex beam. Manifesting purely through electric-dipole interactions and proportional to the paraxial parameter to first order, these topological-charge-dependent light-matter interactions are significantly larger than current ℓ-dependent effects which require material chirality and extremely focused light. The interactions described within represent a novel method for probing the local structure of advanced materials and nanoscale light.