Defined distribution forming in the near diffraction zone based on expansion of finite propagation operator eigenfunctions

This study considers the solution of the inverse diffraction problem for 1D finite (in the spatial and spectral regions) optical signal propagation operator in free space of the near zone (over a distance of several wavelengths). The beam propagation distance and the intervals of input domain and spatial frequency are the parameters of the operator. They change the set of the eigenvalues and eigenfunctions determining the number of degrees of freedom for approximation of a defined distribution. We have solved the inverse problem, namely we have performed the calculation of the input signals ensuring the forming of the defined distributions at various distances.