Technology
How does a laser work?
A laser works by pumping energy into atoms so many of them release identical particles of light at once, then bouncing that light between mirrors so the waves line up. The result is a narrow, single-color beam in which all the light marches in perfect step.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a laser works.
Step by step
- 1Energy (electrical or optical) excites atoms in a 'gain medium', lifting their electrons to a higher energy level.
- 2An excited atom struck by a passing photon emits a second, identical photon — same color, direction, and phase. This is 'stimulated emission'.
- 3Two mirrors form a cavity that reflects the light back and forth, amplifying it as it triggers ever more identical photons.
- 4One mirror is partly transparent, letting a thin, intense, single-color beam escape as the laser's output.
Frequently asked questions
- Why is laser light a single color?
- Every photon comes from the same atomic energy jump, so they all share one wavelength — unlike a bulb, which emits many wavelengths at once.
- What does LASER stand for?
- Light Amplification by Stimulated Emission of Radiation — the process of one photon triggering identical copies of itself.
- Why doesn't a laser spread out like a flashlight?
- Its waves are aligned and travel in nearly the same direction, so the beam stays tight over long distances instead of fanning out.