constant phase modulation as fields of interest $E_{i}(z_{1})$. After propagation through the Fourier lens 5 (see Fig. \[fig:setup\]) the resulting fields $E_{i}(z_{2})$ form a set of Bessel beams. Figure \[fig:bessels\](a) shows the largest ring modulation encoded onto the SLM with the resulting Bessel beam shown in Fig. (b). As this particular Bessel beam comes along with the highest NA compared to the Bessel beams created with smaller ring modulations, the beam shown in Fig. (b) exhibits the smallest central spot of all beams realized in our experiments. The spot size of the Bessel beam featuring the smallest core is denoted as $w_\text{B}$ and used as reference for the measurements presented below. For comparison Figure \[fig:bessels\](c) depicts a circular aperture which is encoded onto the SLM in order to observe the Airy disk (see Fig. (d)). The spot size of the Airy disk is approximately $1.5$ times larger than the core of the reference Bessel beam as expected [@Wang:2008p9893].

![SLM encoded field modulations and resulting beam profiles. (a) Ring mask RGB image as encoded onto the dual panel SLM. (b) Associated Bessel beam created in the CCD camera plane. (c) Aperture RGB image as encoded onto the dual panel SLM. (d) 