Ruby laser and helium-neon laser

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When atoms in a ruby laser (top) emit light, they return to the ground state, where they can absorb light. In the helium-neon laser (bottom) atoms form a new population at a lower exited level that does not absorb the laser light.

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Photo credit: © Encyclopaedia Britannica Inc. / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: atoms, diagrams, helium-neon, laser, lasers, light, maser, ruby