Non-diffractive laser resonators

Summary form only given. Proposes a simple route to the realisation of a Bessel-beam laser based on an optical resonator formed by a conical mirror and a plane mirror. The fascination of Bessel beams (BBs) lies in the fact that, under ideal conditions, they propagate indefinitely without spreading or any other change of shape. Although the distance over which a real Bessel beam can propagate without significant alteration is limited by the aperture of the optical system, a number of practical applications nevertheless exist. For instance, higher-order Bessel beams comprise tubes of light, and the latter have been proposed as potential atom guides in atom-optics experiments. Having laser resonators that produce BBs would be a great convenience.