Cool new theoretical texh

I have recently come up with an idea of how to make a 3D projection or hologram much like princess Leia in Star wars. The device would be based on the precondition that you could get some form of gas to light up if you provide it with just enough energy. It would involve 3 scanning lasers and a hollow tub in which to contain a gas. The lasers would be attached to a scanner much like there are in old TV's and the lasers would scan back and forth to create an image. When all three lasers intersect, they would create a pixel through their combined image. Just a thought that has not been well developed.