(a)–(c) Ratio $\left|g_{n,\mathrm{LA}}^m/g_{n,\mathrm{exa}}^m\right|$ (black solid lines, with circular marks) for a Bessel beam with v = 0 for α = 1° and m = 0, 2 and 5, respectively. (d)–(f) Same as before, now for α = 10°. (g)–(i) Same as (a)–(c), now for α = 30°. For reference purposes, the exact BSCs are also shown (blue dashed lines, with triangular marks), with multiplicative factors being introduced for better visualization. The choice of ρ₀ ≠ 0 allows for non-zero BSCs for m ≠ 0 but has not other implications in the comparison between the plots, since equation (39) does not depend on ρ₀ (had we chosen the same ρ₀, the results would remain unchanged). The beam is assumed to be displaced along the x axis, that is, ϕ₀ = 0 or, equivalently, ρ₀ = x₀.