Phys. Rev. B 99, 241101(R) (2019)

Chiral structures interact differently with left- and right-circularly polarized light — absorbing or scattering either one or the other. Chiral molecules possess an inherent structural handedness and chiral antennas are deliberately designed without mirror symmetry. Sergey Nechayev and Peter Banzer have now shown that chiral states of light can be created from the interaction of achiral light with an achiral nanoparticle.

Although the vector beam in their experiment is not circularly polarized and therefore has no optical chirality, its lack of reflection symmetry makes it geometrically chiral. Similarly, the spherical gold nanoparticle has no geometrical chirality, but it only scatters the electric — not the magnetic — component of the light field, thus breaking electromagnetic duality. The resulting circularly polarized scattered field is evidence that optical chirality is not limited to chiral fields and structures, but can result from more general symmetry breaking.