Fig. 4
From: Coaxial superposition of Bessel beams by discretized spiral axicons
Phase distribution of the on-axis vortex as a function of θ for different N at z=12 mm and with the radius of the circumference of (a) rps=1 μm; (b) rps=5 μm; (c) rps=11 μm. (d) Phase distribution around the SD at xps=yps=26.38 μm for N=6 at z=12 mm with rps as parameter. Note that the phase distributions for different N (a-c) and different rps (d) were each shifted by different multiples Δθ=0.25π for a better overview