Colliding Light Beams

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Science  17 Apr 2009:
Vol. 324, Issue 5925, pp. 315
DOI: 10.1126/science.324.5925.315c

Under normal conditions, photons don't interact with each other very much. For instance, the light beams from two laser pointers pass through each other without trouble. Ramping up the power of the beams, however, changes that somewhat standoffish behavior. High-powered-laser beams can form self-focusing filaments in air that propagate without dispersion. These light bullets or light sabers are finding use in a diverse range of applications from triggering lightning to remote spectroscopic sampling. Finding ways of controlling propagation on the wing rather than tinkering with the laser on the ground would offer much more flexibility.

Bernstein et al. take two high-powered laser beams and collide them. Rather than passing through each other unscathed, the beams couple and exchange energy, up to 7%, with one beam amplifying the other at its own expense. Being able to tune the output of the collision in terms of the energy and frequency distribution of the modified light pulses should provide a powerful and flexible method for remote sensing applications. — ISO

Phys. Rev. Lett. 102, 123902 (2009).

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