Achiral Nanostructures: Perturbative Harmonic Generation and Dichroism Under Vortex and Vector Beams Illumination

Abstract In this study, the nonlinear optical phenomena emerging from the interaction between vortex and vector beams and achiral nanoparticles or nanostructures are investigated. Despite the achiral symmetry of the nanostructure, the interplay between the symmetries of the vortex beam, the nanostructure, and the crystalline lattice of the nanostructure material can result in circular dichroism in the nonlinear regime. A formula is derived that describes the conditions for the appearance of circular dichroism across a broad range of scenarios, taking into account all the symmetries. Building on these findings, the conditions for both linear and nonlinear dichroism when illuminated by vector beams have been determined. This work can provide important insights that can enhance the design of chiral sensors and optical traps, making them more versatile and effective.