Generation of long range low-divergent Gauss–Bessel beams by annihilating optical vortices

Bessel beams are remarkable since they do not diverge. Accordingly, they have numerous applications ranging from precision laser micro-machining to laser particle acceleration. We demonstrate a novel approach for generating long-range Gauss–Bessel beams. A ring-shaped beam is produced by imprinting a vortex with high topological charge in a Gaussian beam. The phase singularities are thereafter removed and the ring-shaped beam focused/Fourier-transformed by a thin lens. This results in a remarkably good realization of a Gauss–Bessel beam. Divergence angles in the microradian range and Gauss–Bessel beam lengths up to 2.5 m behind the focal plane of the lens are demonstrated.