Stimulated emission involves what process in the active medium?

Stimulated emission is a fundamental process in the operation of lasers and involves the transition of excited atoms or molecules back to lower energy states. In this context, when an excited atom or molecule is struck by a photon that has energy matching the difference between its current energy state and a lower energy state, it can emit a second photon. This emitted photon travels in the same direction and phase as the incoming photon, leading to the amplification of light, which is the essence of laser operation.

During this process, the atoms do not absorb additional energy but instead release energy as they transition to a lower energy state. This transition is crucial for creating a coherent and powerful beam of light typical of laser emissions. The efficiency and effectiveness of stimulated emission are key to laser performance, making it vital to understand this process as it relates to how lasers function.