Stimulated Emission
The process in which an incoming photon stimulates an excited atom to drop to a lower state, emitting a second identical photon.
Governing formula
Rate = B₂₁ ρ(ν) N₂
SI unit
s⁻¹ (Transition Rate)
In depth
The emitted photon matches the stimulating photon in frequency, phase, polarization, and direction of propagation. This coherent photon multiplication process forms the foundational basis for LASER operation.
Examples in the real world
Light amplification in lasers producing monochromatic, highly directional, and coherent light beams.