The focusing properties of a Bessel beam generated using an axicon are investigated. The distance between the axicon and the focused lens is tuned to transform the focused beams from bottle beams, with a dark focus surrounded by regions of higher intensity, to hollow beams. The evolutions of these beams are illustrated simply using geometrical structures and the paraxial ray tracing, and are experimentally verified. A specific case in which the focusing behavior approaches that of an ideal Bessel beams is also considered; the experimental results agree with theoretical predictions.
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