Research On The Interactions Between Vortex Structured Light And Chiral Substances

In recent years,vortex structured light with helical phase structure,carrying orbital angular momentum,and exhibiting chiral characteristics,has attracted more and more attention due to its unique physical properties,novel physical effects,as well as various promising potential applications.On the other hand,chiral substances exist widely in nature and the study of chiral substances has a wide range of applications in the fields of life science,drug development,fine chemicals and metamaterials.In this paper,the vortex structured light will be applied to the study of chiral substances.Based on the energy,momentum,spin/ orbital angular momentum and chirality of the vortex structured light interactions with chiral substances,more abundant information of chiral substances may be obtained.The main contents are as follows:1.Description of vortex structured light and its dynamical characteristics.The concept of vortex structured light is introduced and the mathematical expressions of typical vortex structured light are given.Taking Laguerre-Gaussian beam as an example,the explicit expressions of the electromagnetic field components of vortex structured light with general polarization state are derived by introducing the vector potential in the Lorentz gauge,and the expressions of the electromagnetic field components of the tightly focused vortex structured light near the focal plane are derived based on the Richards-Wolf vector diffraction theory.The local dynamical characteristics of Laguerre-Gaussian vortex structured light and its tightly focused case are studied by using the canonical dynamics theory.2.Interactions between vortex structured light and chiral molecules.The chiral effects of the spin / orbital angular momentum of light and their classification mechanism are introduced.The quantized expression of Laguerre-Gaussian vortex structured light is given.The basic theory of the interactions between vortex structured light and chiral molecules is described.The circular dichroism and vortex dichroism of chiral molecules under the illumination of vortex structured light field are numerically analyzed.The mechanism of the Raman optical activity of chiral molecules illuminated by vortex structured light is investigated.The effect of orbital angular momentum of vortex structured light on Raman optical activity is explored.3.Interactions between vortex structured light and chiral particles.The basic theories and methods for the scattering of chiral particles illuminated by vortex structured light are introduced.The method of moment based on surface integral equations is emphasized.The surface integral equations for the scattering of chiral particles are established,and the expressions of impedance matrices after the discretization of surface integral equations are given.The differential scattering cross sections and vortex difference scattering of chiral dielectric particles and chiral structural particles are numerically calculated.The effects of parameters of chiral particles and vortex structured light on the differential scattering cross sections and vortex difference scattering are analyzed in detail.Based on the dipole approximation theory,the optical force of tightly focused vortex light on chiral particles is investigated.4.Interactions between vortex structured light and chiral medium.A full-vector theoretical model is established to describe the reflection and refraction of vortex structured light at an interface between air and a chiral medium.The explicit expressions of the electromagnetic field components of the Laguerre-Gaussian vortex structured light upon reflection and refraction at an interface between air and a chiral medium are derived.The local dynamical characteristics of Laguerre-Gaussian vortex structured light interactions with chiral medium are investigated.The tunable optical chirality of vortex structured light based on chirality medium is analyzed.