You're posting the the gas laser section something about ruby (solid state) and diodes (way different again).
Gamma ray's are photons, you can't build a laser with massless particles traveling at the speed of light...
About the light saber: nope, not possible.
There's an interesting publication here about research into a nuclear laser suitable to instrument use but it does not seem practical for hobby construction. Proposed gamma-ray laser could emit 'nuclear light'