Generation of long-range nondiffracting narrow light beams

A type of nondiffracting narrow light beam that propagates across a long range with a narrow beamwidth is presented. This beam is formed by a distorted concave spherical wave front that can be generated by a Galilean transmitting telescope with an eyepiece that has a spherical aberration. We observed an unusual image with a striped pattern in the laser beam's atmospheric backscatter that provided an opportunity to examine this effect. We demonstrate the mechanism of the generation and the characteristics of the long-range nondiffracting beam. The results show that a nondiffracting core beam with a width of the order of millimeters with a propagation distance of the order of a kilometer is generated by a 10-cm-diameter laser beam.