A stress-induced polarization converter in the form of a zero power optical window or, alternatively, a single element, positive or negative power optical lens, that is subject to a controlled amount of symmetric, peripheral stress. The stress may be provided by appropriate mechanical, thermal, hydraulic, electromagnetic/piezo, annealing/molding, or other known techniques and may be trigonal or four-fold. Axial foci can be created by applying the controlled, symmetric, peripheral stress. The separation distance between the foci can be controlled by controlling the magnitude of the applied symmetric, peripheral stress.