How does optical pumping raise electrons to higher energy levels in a ceramic laser material?

In ceramic laser materials, optical pumping is the process of using an external light source—typically a flash lamp—to excite the material. This process raises electrons within the dopant centers of the ceramic from a stable, low-energy ground state to higher energy levels through the absorption of photons.123

By selectively exciting these atoms, optical pumping creates a population inversion, a condition where more atoms exist in a higher-energy state than in a lower-energy state. In many ceramic lasers, such as the ruby laser, the electrons are initially excited to a short-lived high-energy state before dropping to a metastable state. This metastable state is crucial because it holds the excitation energy, allowing for the subsequent stimulated emission of light as the electrons eventually return to lower energy levels.341