Application Of The Method Of Lines To Shaped Beam Scattering

The study of light scattering is closely related to the development of light source technology.Since the laser was invented,the interaction between laser and particles has been hot studying subject studied by people in the world.The shape,size,refractive index and velocity of the particles can be studied by using the laser with the light scattering spectrometer.The interaction between Gaussian beam,a typical laser beam,and many kinds of particles,including the homogeneous and inhomogeneous particles,has been studied by many researchers,and the research in this area has made some achievements.The Bessel beam,a typical non-diffracting beam,has the obvious difference with the Gaussian beam.Because of its unique propagation characteristics,it has broad application prospects.Therefore,it is of great significance to study the scattering characteristics of different particles under Bessel beam incidence.In this thesis,the modified method of lines(MMOL)is used to study the scattering characteristics of Gaussian beam and Bessel beam.As a semi-analytical method,the MMOL has high precision,and it can reduce the difficulty of solving the problem by reducing the dimension of the partial differential equation.The main research works of this thesisare summarized as follows:1.The scattering characteristics of the cylindrical particles under plane wave incidence are analyzed by the MMOL.By comparing the numerical results with the analytical results,it is found that the electric field distribution is almost the same.It can be seen that the MMOL has very high accuracy,and the solving process is relatively simple.The MMOL is very useful to deal with the electromagnetic scattering calculation.2.Taking into account the Gaussian beam incidence in the two-dimensional case,the angular spectrum expansion method is used to expand the Gaussian beam into several plane waves with different amplitudes and different incident directions.In this thesis,the MMOL is used to analyze the scattering process of each plane wave in a conducting cylindrical particle,and the scattering field of each plane wave is superposed into the scattering field of the incident Gaussian beam.The numerical results are in good agreement with those obtained by the analytical method,and the method is proved to be correct.3.The scattering characteristics of the conducting cylindrical particles under the incident of Bessel beam are analyzed by the MMOL,and the cylinders with various cross section,including the Chebyshev particles,prolate spheroid and other non-circular cylindrical particle,are considered.The effects of half cone angles on the scattering characteristics of the scalar Bessel beam are also discussed.The Bessel beam is deduced to a plane wave,and the numerical results are compared with the analytical results.4.The scattering characteristics of a dielectric cylinder placed in a Bessel beam are studied by the MMOL.The effects of the cross section of particles,the half-cone angle and order of the Bessel beam to the internal and external electric fields are discussed.