Asian Journal of Physics Vol. 30 Nos 8 & 9 (2021) 1283-1288

Controlling the topological charge of superposition of Bessel-Gaussian beams
V V Kotlyar, A А Kovalev and A G Nalimov


We show that by continuously varying the amplitude of a constituent beam in the superposition of two Bessel-Gaussian (BG) beams with topological charges (TC) m and n (m < n) the TC of the entire superposition can be controlled. It is shown that if the amplitude of the constituent beam with TC n is larger than that of the beam with TC m, the superposition contains n optical vortices (OV), namely, an OV with TC m in the form of on-axis isolated intensity null and n – m simple OVs with TC 1 localized off-center along rays that make with one another angles of 2π/(n – m). By getting the amplitudes of the BG beams closer to each other, n – m simple OVs are moved away from the beam center along the said rays. At equal amplitudes, n – m OVs are removed to infinity and TC of the superposition equals (n + m)/2. If the amplitude of the beam with TC m is larger than that of the beam with TC n, the only m-fold on-axis intensity null is present in the superposition. Similarly, TC of the superposition can be controlled by changing the scaling factor of one of the constituent BG beams. © Anita Publications. All rights reserved.
Keywords: Topological charge, Bessel -Gaussian beams, Optical vortices, Orbital angular momentum.

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