Actually I work with lasers for a living! Surprise, Surprise Well anyway, trying to not get to technical, a lasers power is determined by the material that is used to jump the electrons to their excited state which in turn creates the light that is used for the laser. the second is the focus of the laser (their are others but these are the prominent), if you take a LAG laser and havea beam that is 6 inches in diameter it's relativly harmless, focus it too 6 microns and I can take your finger off. Laser "light" is not dense and doesn't "cut" persay, in most cases it vaporizes the material it comes in contact with becasue of the intense heat that the laser generates. I know what your saying is that the sabres may act as an excelerator that would casue the protons to speed upto the rate that they are right next to one another and compacting them. while this may create a pretty intense and powerful laser,I don't believe it would create the density we are lookin for. For it to be a solid beam like we see in the movies we are lookin for a molecular bond that would hold the lightsabres beam together with no distortion. A bond of this type is really only found in solids. If the sabre blade takes the property of a solid that means the opposite would happen on the molecular level it would all slow down thus allowing a bond to form between molecules and slowing light down to that speed is Impossible.
While I do work with lasers for a living I am by no means an expert, Any Noble Winning Physicists out there?