Generation of optical 3D unpolarized lattices in a tightly focused random beam

We study the three-dimensional (3D) polarization properties of a tightly focused partially coherent vector beam whose initial spatial coherence structure exhibits a lattice distribution. By examining the 3D degree of polarization and the polarimetric dimension of the tightly focused field, we demonstrate that this initial spatial coherence structure induces a 3D isotropically unpolarized beam lattice in the focal plane. Along the longitudinal direction, we observe the formation of nearly 3D unpolarized channels spanning 16 wavelengths in length near the focal region. We demonstrate that the spatial distribution of the 3D unpolarized lattice can be conveniently controlled through engineering the spatial coherence structure of the incident beam.