Experimental realization of focal field engineering of the azimuthally polarized beams modulated by multi-azimuthal masks

This paper experimentally investigates the controlling of a focal field of azimuthally polarized (AP) Gaussian beams with multi-azimuthal masks. Based on the angular diffraction theory, an explicit model is established to describe the intensity and polarization distributions of the focal fields. It reveals that the focal fields of the modulated AP beams are closely related to the mask structure. By designing the parameters of the mask structure, we could consciously manage the intensity and polarization distributions of the focal fields of an AP Gaussian beam. Our experimental results also demonstrate the feasibility of controlling focal field characteristics by engineering the mask structure, and suggest an effective approach for manipulating the focal field of vector beams.