Interaction of light carrying orbital angular momentum with a chiral dipolar scatterer

The capability to distinguish the handedness of circularly polarized light is a well known intrinsic property of a chiral nanostructure. It is a long standing controversial debate, however, whether a chiral object can also sense the vorticity, or the orbital angular momentum OAM , of a light field. Since OAM is a non local property, it seems rather counter intuitive that a point like chiral object could be able to distinguish the sense of the wave front of light carrying OAM. Here, we show that a dipolar chiral nanostructure is indeed capable of distinguishing the sign of the phase vortex of the incoming light beam. To this end, we take advantage of the conversion of the sign of OAM, carried by a linearly polarized Laguerre Gaussian beam, into the sign of optical chirality upon tight focusing. Our study provides for a deeper insight into the discussion of chiral light matter interactions and the respective role of OAM