![Four-level and three-level laser gain media, reabsorption, crystals, glass, quasi-three-level, solid-state lasers, Yb:YAG Four-level and three-level laser gain media, reabsorption, crystals, glass, quasi-three-level, solid-state lasers, Yb:YAG](https://www.rp-photonics.com/previews/four_level_and_three_level_laser_gain_media.png)
Four-level and three-level laser gain media, reabsorption, crystals, glass, quasi-three-level, solid-state lasers, Yb:YAG
![Why not just pump directly to the $3^\mathrm{rd}$ level directly in a $4$-level laser system? - Physics Stack Exchange Why not just pump directly to the $3^\mathrm{rd}$ level directly in a $4$-level laser system? - Physics Stack Exchange](https://i.stack.imgur.com/B2Ouu.png)
Why not just pump directly to the $3^\mathrm{rd}$ level directly in a $4$-level laser system? - Physics Stack Exchange
1.: Simplified 4-level (left) and 3-level (right) system. The 3-level... | Download Scientific Diagram
![a) Energy level diagram of a three-level laser system depicting the... | Download Scientific Diagram a) Energy level diagram of a three-level laser system depicting the... | Download Scientific Diagram](https://www.researchgate.net/publication/310451688/figure/fig1/AS:429396168318979@1479387432534/a-Energy-level-diagram-of-a-three-level-laser-system-depicting-the-various-transition.png)