laser theory

Laser theory describes how a device amplifies light through a process called stimulated emission. When atoms in a medium (like a gas, crystal, or liquid) are energized by an external source, they reach an excited state. As they return to a lower energy level, they emit photons. In a laser, these photons stimulate other excited atoms to emit additional photons with identical wavelength, phase, and direction. By trapping these photons in a resonant cavity, the process builds up a coherent, intense beam of light. This principles of controlled energy input, stimulated emission, and feedback enable the production of focused, high-quality laser beams.