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Lasers Approach Their Ultimate Intensity Limit
Flash Modin writes "Death Star style superlasers? Don't bet on it. High-power lasers currently in development appear to be nearing the theoretical laser intensity limit, according to new research set to be published in the journal Physical Review Letters. Ultra-high-energy laser fields can actually convert their light into matter as shown in the late '90s at the Stanford Linear Accelerator (SLAC). This process creates an 'avalanche-like electromagnetic cascade' (also known as sparking the vacuum) capable of destroying a laser field. Physicists thought it might be a problem for lasers eventually, but this work indicates the technology is much closer to its limit than researchers believed. A preprint is available here."
Actually, from what I can see, the blaster, the death star's beam, the lightsaber and even the beam weapons on the clone wars gunship turrets seem to work on something other than "laser." They seem to operate on energized particles or energy that is transformed into a mass-like state. In the case of the death star, it would seem to explain why merging many beams from different angles could actually result in a single beam going in yet another angle.
In any case, you can see blaster bolts travel... they seem to fly at around arrow speed. The fact that they emit light leads people to think "laser" when in reality, you can't see a laser in most cases unless there is interference in the air. (BTW, did you ever notice that headlights seem to be less effective at night after a rainfall? That's because the roads are wet and more reflective... the light gets reflected away from your eyes and so you can't see the light bounce back to your eyes.)
Worse still, the term "laser sword" is actually used in Star Wars which doesn't help things at all. Young Anakin identifies Qui Gon as a Jedi because of his "laser sword." On one hand it is forgiveable because he's a kid, but on the other hand, he's a genius kid and should know better. In any case, lightsabers have a shadow (because of some sloppy film editing) but ostensibly because they are not lasers but an energy/matter transition state where energy is made to behave as matter. (Though only shown in games and cartoons, energy "bridges" are used to create temporary walkways using a technology similar to that used in lightsabers)
It's all fiction anyway, but it helps to try to understand the technology imagined in these fictions. The technologies imagined in SciFi are quite often candidate for implementation in our present or near future.