Scattering of arbitrarily incident Gaussian beams by fractal soot aggregates

A hybridization of the finite element and boundary integral methods is applied to the study of light scattering by fractal soot aggregates illuminated by Gaussian beams with arbitrary incidence. In particular, the Davis–Barton fifth-order approximation in combination with rotation Euler angles is employed to represent the arbitrarily incident Gaussian beams. The finite element method is used to obtain the solution of the vector wave equation inside each primary particle and the boundary integral equations are applied on the surfaces of all the particles as a global boundary condition. The resultant matrix equation is solved by an iterative method, where the multilevel fast multipole algorithm can be employed to speed up the matrix–vector multiplication. Some numerical results are included to illustrate the validity of the present method and to show the scattering behaviors of fractal soot aggregates when they are illuminated by Gaussian beams. (paper)