Scattering Of A Dielectric Sphere By A Polarized Airy Beam And Mechanical Effects

The modern industry's requirements of multi-function,high compactness,and ultraprecision have advanced the development of precision optical instruments.Optical manipulation,namely,the manipulation of micro particles by the mechanical effect of light,is one of the trend of future development.The parabolic trajectory of the Airy beam itself makes it possible to bypass obstacles and achieve optical manipulation with more possibilities when used as a light source.In addition,the limited diffraction of Airy beams also eliminates the limitation of diffraction on the precision of optical instruments to a certain extent.The Generalized Lorenz-Mie Theory(GLMT)can accurately calculate the electromagnetic scattering characteristics of spherical particles of arbitrary size when irradiated by any beam.As long as the beam shape coefficients(BSCs)of an incident beam is determined,the scattering characteristics of particles can be calculated.Based on GLMT and Maxwell's stress tensor method,the paper mainly study the scattering and resonance scattering characteristics and mechanical effect when a polarized Airy beam illuminates a a dielectric sphere.The main research work are as follows:1.Using the angular spectrum expansion method(VASDM)and the multipole expansion method involving vector spherical wave functions(VSWFs),the general expression of the BSCs of the vector Airy beam is derived.The resonance scattering characteristics are calculated using the GLMT by subtracting a non-resonant background of a perfectly conducting impenetrable sphere.Resonance scattering is the scattering obtained by treating a perfect conductive sphere as a non-resonant background,and then subtracting the background from the dielectric sphere.Numerical simulation analysis shows that the extinction(scattering)efficiency,resonance scattering efficiency and conducting extinction(scattering)efficiency of the dielectric sphere are always larger than zero,while the interference scattering efficiency may take a negative value.The polarization state of the Airy beam affects the direction and distribution of the normalized intensity lobe.2.The optical force of a dielectric lossless sphere illuminated by vector Airy beams of various polarizations is thoroughly studied.Numerical computations are performed in order to analyze the effects of the dimensionless size parameters of the dielectric sphere,as well as the transverse scale and the attenuation parameter of the Airy beam on the transversal and longitudinal components of the optical force.The polarization states considered include linear,mixed,circular,azimuthal and radial polarizations.Studies have shown that when the vector Airy beam irradiates the dielectricsphere,the particle is trapped into the main caustic or side lobes by the transverse optical force,and moves along the parabolic trajectory with action of the longitudinal optical force.The curves of the transverse component Fyu and the longitudinal component Fzu of the optical force have similar changing trends when the incident beam is linear,circular,and mixed polarizations.The same rule also applies to the azimuthally and radially polarized Airy beams.3.The transverse and longitudinal components of optical torque are theoretically evaluated and numerically simulated with an emphasis on the transverse scale ?0 and attenuation parameter ? of the incident Airy beam.The influence of the seven selected polarization states is still considered.The research results show that the transverse scale,attenuation parameters,and polarization states will all affect the distribution and amplitude of the transverse and longitudinal torques.It providing another degree of mechanical freedom for optical manipulation in addition to the optical force,and makes it possible to make particle rotation.For circularly polarized Airy beams,the change of the circularly polarized rotation direction will cause the longitudinal torque on the particle to reverse in direction and remain unchanged in amplitude at once.