What role do dopants play in solid-state lasers?

Dopants play a crucial role in solid-state lasers by creating energy levels that enable laser action to occur. In a solid-state laser, the host material, which is typically a crystal or glass, does not have the appropriate energy levels for lasing. By incorporating dopants—such as rare earth or transition metal ions—into the host material, additional energy states are introduced. When the laser system is pumped with energy, typically from a flashlamp or another light source, the dopants absorb this energy and get excited to higher energy levels.

As the dopants return to their lower energy states, they can emit photons, and if these emitted photons have the right properties, they can stimulate further emissions from other excited dopant ions. This process creates the chain reaction necessary for laser amplification. Thus, the presence of dopants is essential in determining not just the lasing capabilities of the solid-state laser, but also its characteristics such as wavelength and efficiency.