Solving the inverse problem of high numerical aperture focusing using   vector Slepian harmonics and vector Slepian multipole fields
  A technique using vector Slepian harmonics and multipole fields is presented for a general treatment of the inverse problem of high numerical aperture focusing. A prescribed intensity distribution or electric field distribution in the focal volume is approximated using numerical optimization and the corresponding illuminating field at the entrance pupil is constructed. Three examples from the recent literature have been chosen to illustrate the method. 
Korn\'el Jahn, N\'andor Bokor
physics.optics