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Four-level and three-level laser gain media, explained by RP Photonics Encyclopedia; reabsorption, crystals, glass, quasi-three-level, solid-state lasers, Yb:YAG
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radiation - Would a laser with four possible energy levels be better than three? - Physics Stack Exchange
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Four-level and three-level laser gain media, explained by RP Photonics Encyclopedia; reabsorption, crystals, glass, quasi-three-level, solid-state lasers, Yb:YAG
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