Dynamical generation of multiple focal spot pairs with controllable position and polarization

We report a flexible method to dynamically generate multiple sub-wavelength focal spot pairs with adjustable polarization, position and number at the focal plane of a high numerical aperture (NA) objective lens. The desired incident field on the pupil plane can be analytically derived by employing the time-reversed method combined with the dipole antenna radiation theory. The numerical simulations of the corresponding tightly focused field are conducted using the Richards-Wolf vectorial diffraction theory. The validity of the presented method is demonstrated through experimental generation of several designed pupil fields with a versatile vectorial optical field generator and characterization of the produced focused fields with Stokes parameter measurements.