  We report,to the best of our knowledge, the first observation of
concentrating paraxial beams of light in a linear nondispersive medium. We have
generated this intriguing class of light beams, recently predicted by one of
us, in both one- and two-dimensional configurations. As we demonstrate in our
experiments, these concentrating beams display unconventional features, such as
the ability to strongly focus in the focal spot of a thin lens like a plane
wave, while keeping their total energy finite.
