Stimulated emission is a quantum process in which an incoming photon prompts an excited atom or molecule to emit a second photon that is identical in energy, phase, direction, and polarization.
Key Features:
- Triggering Photon: An incident photon with energy matching the gap between the excited and lower states initiates the emission.
- Coherence: The emitted photon is a perfect copy of the triggering one, making the light coherent.
- Amplification: This process can cascade, producing a beam of many identical photons—light amplification.
Role in Lasers:
- “Laser” stands for: Light Amplification by Stimulated Emission of Radiation.
- Population inversion (more atoms in excited states than in lower ones) is essential for sustained stimulated emission in lasers.
- The process results in a highly focused, monochromatic, and coherent beam.
Stimulated emission is what allows lasers to generate powerful, precise, and controllable beams of light used in applications ranging from medicine and communication to manufacturing and scientific research.