Bessel-like beams with z-dependent cone angles.

The conventional means of generating Bessel-Gauss beams by axicons in the laboratory results in the distinct disadvantage of an abrupt change in intensity at the boundary of the non-diffracting region. We outline theoretically and then demonstrate experimentally a concept for the creation of Bessel-like beams that have a z-dependent cone angle, thereby allowing for a far greater quasi non-diffracting propagation region.