We analyze the evolution of the vortex and asymmetrical parts of the orbital angular momentum during its propagation through separable first-order optical systems. We obtain that the evolution of the vortex part depends only upon the parameters a_x, a_y, b_x, and b_y of the ray transformation matrix, and that isotropic systems with the same ratio b/a produce the same change of the vortex part of the orbital angular momentum. Finally, it is shown that when light propagates through an optical fiber with a quadratic refractive index dependence, the vortex part of the orbital angular momentum cannot change its sign more than four times per period.

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http://www.opticsinfobase.org/abstract.cfm?URI=ol-29-14-1587

To: Papers by Martin J. Bastiaans