Research On Spin Hall Effect Of Light And Its Control In Dielectric Thin Film Structure

The spin Hall effect(SHE)of light is a transport phenomenon that two spin components of a light beam acquire opposite transverse displacements in the direction perpendicular to the plane of incidence when a Gaussian light beam propagates through an inhomogeneous medium.The SHE of light has promising applications in precision measurement,nano-optics and quantum information.However,the SHE of light is a weak effect,the induced spin-dependent shift is on the subwavelength scale,so that the development and application of the SHE of light are limited.It is worth mentioning that the SHE of light can be tuned by refractive index gradient,and the dielectric thin film structure can artificially manufacture different refractive index gradients,so it can be used to manipulate the SHE of light.In this paper,based on the study of the polarization state conversion,the regulation of the spin-dependent splitting is studied at the air-glass.The enhancement of the SHE of light in the metal thin film structure is also studied by transfer matrix method.Therefore,the regulation and enhancement of the SHE of light is realized.Some results are obtained as follow.Firstly,a conversion approach based on waveplates on the Poincaré sphere can be obtained.It is found that the half-wave plate can realize the conversion of arbitrary longitude on a certain fixed latitude of the two different hemispheres.In addition,the quarter-wave plate can not only convert from any arbitrary point on the sphere to the equator,but convert from any point on the equator to the 0 longitude.On the basis of the above laws,the conversion between arbitrary polarization states can be realized by using two half-wave plates and two quarter-wave plates.Secondly,the influence of the polarization angle and the incident angle on the spin-dependent splitting induced by SHE of light and in-plane spin separation of light has been studied when a Gaussian light is reflected from an air-glass interface.It's revealed that there is a spin-splitting rotation phenomenon with the increase of the polarization angle.We also find that the spin-splitting rotation takes place as a result of the various proportions of displacement induced by SHE of light and in-plane spin separation of light.The speed and direction of the spin-splitting rotation can be manipulated by incident angle.Finally,a metal dielectric thin film structure composed of BK7 glass,alloy film,and air is proposed to realize the enhancement of the SHE of light,and the influence of the permittivity of alloy film on SHE of light is also explored.It's shown that the resonant angle of the surface plasmon resonance is mainly influenced by the real part of the permittivity of alloy film,while the imaginary part has little influence on it.The SHE of light can be greatly enhanced when the permittivity of alloy film is at the resonance angles.At the same time,it is also found that changing the permittivity of the alloy film can further enhance the SHE of light at a fixed incident angle when compared with the value in a pure nanometal structure.