Beam maintains peak intensity within absorbing medium

It is well known that a coherent light beam with the proper Bessel-function intensity cross section can have a high-intensity central core that propagates for certain distances without spreading-a phenomenon termed pseudo nondiffraction (which has practical uses for laser-assisted alignment).

It is well known that a coherent light beam with the proper Bessel-function intensity cross section can have a high-intensity central core that propagates for certain distances without spreading-a phenomenon termed pseudo nondiffraction (which has practical uses for laser-assisted alignment). Now, researchers at the State University of Campinas (Campinas, Brazil) have produced (although as yet only in theory) a pseudo-nondiffracting light beam that maintains a constant peak intensity in its central core as it propagates through an absorbing medium.

The beam does this not by defying the laws of physics, but by gradually shifting energy from its low-intensity wings to its central core as the beam propagates. As in ordinary pseudo-diffracting beams, the effect falls apart after the beam propagates a certain distance. In a simulation, 308‑nm light from a xenon chloride excimer laser was formed into the Bessel profile and entered an absorbing medium that had a penetration depth of 5 cm. The beam traveled 25 cm through the medium (five times the penetration depth) while maintaining a constant peak intensity. Contact Michel Zamboni-Rached at [email protected]br.

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