As has been said, light doesn't stop in midair.
Also, two beams of light don't go "clunk" when they hit each other.
The lightsabre is in fact an infinitely-thin, virtually one-dimensional force field generated by machinery in the hilt. It's so thin that as it moves, or as air moves past it, subatomic particles are sliced in half, evaporating in bursts of pure energy.
The energy is generated in the form of ultra-ultra short wave radiation, shorter than gamma rays and highly dangerous. Switching on the lightsabre would be a hightech way of committing suicide if it were not for a second field, surrounding the first. This second field channels some of the energy into the hilt, recharging the battery and making the whole thing self-powered. The remainder is converted into visible light. This makes it safe for the user and means that he/she can see where the otherwise invisible "blade" is at any time - an important feature if you want to avoid slicing anything and everything around you. The frequency of the emitted light is tunable, so the users can set the blade colour to whatever suits them.
The technology behind all this is subject to a level #1 interdict, given the current state of civilisation on Earth. Sorry, people. You'll have to show you're grown up before you can be allowed to play with this stuff.
