Generation of propagation-invariant vector beams with square array by use of 2D binary phase mask and pentagonal prism

In this paper, we realize the generation of propagation-invariant vector beams with square array by use of a 2D binary phase mask and pentagonal prism in a typical Mach-Zehnder optical system. The binary phase mask set in the optical system is perpendicular to the optical axis, and its periodic orientation is 45° relative to the horizontal and vertical directions. One polarizer was used to produce the linearly polarized beam with the angle of 45° relative to the horizontal and vertical directions. One mirror in the Mach-Zehnder optical system was replaced by a pentagonal prism, as the light will be reflected twice inside the pentagonal prism. The intensity distribution of the two branches with the mirror and pentagonal prism have mirror symmetry, and the output optical field of the two branches has an orthogonal polarization state. By adjusting the position of the phase plate accordingly, the total optical field of the two branches can form a vector beam with a square array. The experimental results coincide with the simulation results very well and demonstrate the feasibility of this method.