Rule #1 in all things Lucasfilm: Cool always beats Physics. Any attempt to explain the tech in Star Wars is after the fact attempts to try and explain what the film makers thought looked spiffy.
Lucas: I want swords made out of lasers! And we could have them be able to deflect laser beams! So cool!
Science Dude: How the heck would that work?
Lucas: Who cares. It's going to be freaking awesome!