Fig. 1. Scheme of TC measurement of a vortex beam (l = 3 exampled) with a screen plate S located at the x₀−y₀ plane (z = 0). The cross section of the plate is shown at the bottom left. The diffraction patterns aligned along the z axis illustrate the evolution of the OV edge diffraction.

Fig. 2. Simulated intensity profiles of OV beams edge-diffracted by an opaque screen for (a) l = −2 to 2 in steps of 1, (b) r¯=0–2 in steps of 0.5, (c) θ_s = 0°–180° in steps of 45°, and (d) z¯=0.05, 0.1, 0.2, 0.4, 1, respectively. The general case is l = 3, r¯=1, θ_s = 0°, and z¯=0.1. Auxiliary red dashed lines indicate the dark fringes. Hatched area shows the position of the plate, and the yellow arrow points in the direction of the fork-shaped fringe. The intensity distribution is normalized.

Fig. 3. Simulated intensity profiles at l = 3, r¯=1, z¯=0.1 after edge diffraction by a translucent plate with (a) the transparency α = 0–1 in steps of 0.25, (b) the normalized thickness d^¯=0–4 in steps of 1, and (c) the angle between two surfaces of the plate β = −6° to 6° in steps of 3°. The general case is α = 1, d^¯=4, and β = 0°.

Fig. 4. (a) Experimental setup for generating the OV beam using SLM1 loaded with (b) fork-shaped blazed gratings and measuring the TC using SLM2 loaded with (c) a phase step. λ/2, half-wave plate; SLM, spatial light modulator; S, an opaque screen in Fig. 1 in the case of α = 0; CCD, charge coupled device.

Fig. 5. Experimental intensity profiles of the OV beam (l = 3) at z¯ of (a) 0.05, (b), (d) 0.1, and (c) 0.2 after edge diffraction by (a)–(c) an opaque or (d) a transparent plate (d^¯=4) at r¯=0–1.5 in steps of 0.5 for column 1–4, respectively.

Fig. 6. Experimental intensity profiles for (a) unperturbed and (b) opaque screen (r¯=1, z¯=0.1) edge-diffracted vortex beams with topological charge −40 and +40 for columns 1 and 2, respectively. Corresponding enhanced patterns are shown in (c), where the inset with the yellow box shows the partially scaled image, and the cambered red and blue cross sections of the intensity indicate (d) the number of upside and downside fringes, respectively.