, as can be seen in nuclear explosions

"At high laser intensities interaction of the created electron and positron with the laser field can lead to production of multiple new particles and thus to formation of an avalanche-like electromagnetic cascade."

In 1997, an experiment at SLAC sent 47-billion eV electrons from its 2 mile long accelerator and collided them with a one trillion watt green laser to create a monstrous electromagnetic field. When the electrons and the photons from the laser impacted, they created higher energy gamma-ray photons, these gamma-ray photons then collided with photons in the laser beam again and shattered the vacuum as matter was spontaneously created from light within the experiment.Creating light from matter is rather ordinary in terms of physics. But the SLAC experiment was the first to produce the opposite, and while the effect had been expected for some 50 years, the equipment hadn't existed to test it experimentally. It is known amongst physicists as creating "spark in a vacuum." When the electromagnetic field has enough energy, light becomes matter as a positron-electron pair is produced.The SLAC experiment was just a singular event, but as lasers reach higher intensities the electric fields produced will increase as well and the team says that when they reach a critical intensity a cascade effect will occur as a result. The electron-positron pair is accelerated by the laser field itself at such high energies that they emit photons capable of spawning new pairs and continuing the process. In fact, their estimations indicate that even a single such pair can completely destroy the laser field as the energy created from the pairs can equal that of the laser.From the paper (available in preprint on the arXiv ):Physicists have suspected this cascade effect could limit the intensity of lasers, but these new calculations show that the effect will likely be seen in lasers already being built like the European laser projects ELI (Extreme Light Infrastructure) and XFEL (X-ray Laser Project).