In laser physics, what is the term "gain" used to describe?

The term "gain" in laser physics refers specifically to the increase in the intensity of light as it travels through the gain medium. This process occurs when the medium is excited, providing stimulation to emit photons, which amplifies the light. As the light passes through the gain medium, it experiences an amplification due to the stimulated emission of radiation, which is a fundamental principle of laser operation.

The gain is essential because it indicates how effective the laser medium is at amplifying the light, which is critical for producing coherent and focused laser beams. A successful laser requires a gain medium that is capable of efficiently increasing the intensity of the light, ultimately leading to the generation of a powerful and focused output.