Effective method for solving the diffraction problem

Allowance is made for large-angle diffraction in the near-field zone where such diffraction perturbs a smooth amplitude-phase distribution and the results in depolarization of laser radiation travelling along systems with stops. The Maxwell equations are solved subject to the Kirchhoff–Kottler boundary conditions using the Rubinowicz transformation. The method is time-consuming, which is typical of the paraxial approximation, but it does provide solution of the problem for arbitrary diffraction angles and thus an opportunity to determine the angular dependences of the components of the electromagnetic field, which cannot be done employing traditional scalar methods.