An axicon lens is flat on one side, conical on the other. After passing through the flat surface, a beam of light with a Gaussian profile emerges from the conical surface with a profile that looks approximately like a zeroth-order Bessel function. Bessel beams interest physicists because of a remarkable property: Thanks to the way the beams’ energy and phase components are spread in space, the beams barely diffract—even around certain obstacles. Now, Florian Fahrbach, Philipp Simon, and Alexander Rohrbach of the University of Freiburg in Germany have demonstrated that
Bessel beams can propagate without significant diffraction through inhomogeneous media. The accompanying figure shows the intensity of fluorescence emitted by a transparent fluorescent gel when three kinds of beam passed through from left to right: a sheet-shaped beam from a cylindrical lens, a Gaussian beam scanned from top to bottom, and a Bessel beam scanned from top to bottom. The...
