Scattering And Optical Forces Of Complex Spherical Particles By Vector Shaped Beams

The interactions of the chiral and anisotropic medium with laser beam have been of great significance due to its wide applications in microwave antennas,biological diagnosis,and optical manipulation etc.The research on vector shaped beam almost focused on its generation,modulation,propagation and the scattering properties by isotropic particles.The interactions of vector shaped beam with chiral and anisotropic medium are still of great theoretical significance and wide applications.Based on the analytical method,this thesis researches on the scattering characteristics of chiral sphere and anisotropic sphere by zero and higher order Bessel beam,higher order Hermite-Gaussian beam,higher order Laguerre-Gaussian vortex beam and higher order Bessel vortex beam in different polarization,and the radiation force and torque exerted on a uniaxial anisotropic sphere by higher order Laguerre-Gaussian vortex beam and higher order Bessel vortex beam.The main contributions and results are as follows:1.Using the superposition of plane wave along the conical surface and the vector wave method,the expansion expression and expansion coefficients of axicon-generated zero order Bessel beam,zero order Bessel beam and higher order Bessel beam are derived.Based on the eigenmode expansion of the internal field of chiral sphere and the electromagnetic scattering theory,the scattering of a chiral sphere by zero order Bessel beam are obtained.The scattering of anisotropic sphere by higher order Bessel beam are also derived based on the internal filed expansion of anisotropic sphere in terms of spherical vector wave functions.The effects of conical angle,beam center position,chiral parameter and particle size on the scattering intensity are numerically analyzed.The influence of topological charge,conical angle,oblique angle,anisotropic permittivity and permeability tensor elements and particle size on the scattering field are discussed in detail.2.With the complex source point method and coordinate rotation theory applied,a general expansion for an arbitrarily incident higher order Hermite-Gaussian beam in terms of spherical vector wave functions is derived,and its convergence is numerically discussed.Based on the internal field eigenmode expansion of anisotropic sphere and the scattered field expression,with the continuous tangential boundary conditions applied,the analytical solution to the scattering of a uniaxial anisotropic,plasma and ferrite anisotropic sphere by arbitrarily incident higher order Hermite-Gaussian beam is obtained.Two eigenmodes inside the uniaxial anisotropic sphere are characterized.The influences of the beam mode,oblique incident angles,permittivity and permeability tensors,and sphere radius on the scattered field are analyzed numerically.3.Based on the expansion of higher order Hermite-Gaussian beam by complex source point method and the transformation between Hermite polynomial and Laguerre polynomial,the expansion expression of higher order Laguerre-Gaussian vortex beam is derived.With the continuous tangential boundary condition applied,the scattering coefficients and internal field expansion coefficients are obtained.The scattering of a chiral sphere by higher order Laguerre-Gaussian vortex beam and the internal eigenmode distribution are characterized.The numerical results of the incident beam expansion coefficients convergence and the scattered field comparison with the reference prove the validity of the validity of the theoretical analysis and computation codes.The influences of the radial beam mode,topological charge,beam width,chirality and the spherical sized on the scattered field are numerically discussed.4.An analytical solution to the scattering,radiation force and torque on a uniaxial anisotropic sphere by a higher order Laguerre-Gaussian vortex beam is presented.Within the framework of the electromagnetic scattering theory,and based on expansion expression of incident higher order Laguerre-Gaussian vortex beam,internal of uniaxial anisotropic sphere,and the scattered field in terms of spherical vector wave functions,the scattered field expression is derived with the continuous boundary condition applied.According to the classic Maxwell electromagnetic theory and the conservation of momentum and angular momentum,the radiation force and torque are expressed with the incident coefficients and scattering coefficients.The effects of the radial beam mode,topological charge,permittivity and permeability tensor elements and particle size on the radiation force and torque are numerically analyzed.5.Using the angle spectrum expansion,the electromagnetic field of the linearly polarized,circularly polarized,radially polarized,azimuthally polarized and unpolarized higher order Bessel vortex beam are derived.Based on the orthogonality the exponential function and associated Legendre function,the integral expression of the inhomogeneous polarized higher order Bessel vortex beam expansion coefficients are obtained.Analytical expressions of the scattering field,transverse and axial radiation force and torque exerted on a uniaxial anisotropic sphere by higher order Bessel vortex beam are derive.The effects of polarization,topological charge,anisotropic dielectric parameters and particle size on scattering intensity,radiation force and torque are numerically discussed.