Enhanced Photonic Spin Splitting By Orbital Angular Momentum

In recent years,the photonic spin splitting,as a new phenomenon has attracted significant attention.The photonic spin splitting is a physical phenomenon in which a photon with opposite spin angular momentum will shift toward opposite directions when a linearly polarized bounded beam is reflected or refracted at an interface of medium.There are two kinds of spin splitting.One is occurs within the plane of incidence,the other in the direction perpendicular to the incident plane which is also known as the spin Hall effect of light.The photonic spin splitting provides a new way to manipulate photons.It has important application prospects in nano-optics,semiconductor physics,high energy physics and quantum information.Vortex beam is a beam carrying orbital angular momentum,which has a unique annular light intensity distribution and a unique spiral phase wavefront.Much attention has been paid to the research of the vortex beam due to its potential application value in the fields of particle manipulation,optical communication and so on.In this paper,the photonic spin splitting in parallel and perpendicular directions to the incident plane are studied,respectively.The influence of orbital angular momentum on the photonic spin splitting is also studied.The research results are as follows:Firstly,we have analyzed the photonic spin splitting of transmitted light beam within the incident plane by considering high-order Laguerre-Gaussian beams transmitting through a thin transparent medium.The upper bound of the spin splitting is found to be|?|w₀/(|?|+1)^1/2,where?and w₀ are the incident topological charge and beam waist,respectively.The spin splitting of the transmitted beam can reach more than 0.99 of the upper bound in the cases of both the horizontal and vertical incident polarization states when the permittivity of the transparent medium is near zero.Moreover,the spin splitting enhanced by the increase of topological charge of the incident light beam.Secondly,the spin splitting of reflected light beams on chiral metamaterial in the direction perpendicular to the incident plane are investigated systematically.When a linearly polarized light beam is reflected at an air-chiral interface,the asymmetric photonic spin splitting will occur in the direction perpendicular to the incident plane,due to the spin-orbit interaction of light.Furthermore,it is found that the maximum photonic spin splitting occurs near the intersection of reflection coefficients|r_pp|and|r_sp|.In addition,the effect of orbital angular momentum on asymmetric photonic spin splitting is also studied when the incident light is a vortex light beam.The asymmetric spin splitting of the reflected light beams can be controlled not only by the chirality of the material,but also by the orbital angular momentum of the incident beam.