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How does a laser work?
Quick answer
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.
Step by step
- Energy (electrical or optical) excites atoms in a 'gain medium', lifting their electrons to a higher energy level.
- An excited atom struck by a passing photon emits a second, identical photon — same color, direction, and phase. This is 'stimulated emission'.
- Two mirrors form a cavity that reflects the light back and forth, amplifying it as it triggers ever more identical photons.
- One mirror is partly transparent, letting a thin, intense, single-color beam escape as the laser's output.
People also ask
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.
What makes laser light special?
Its waves are all the same color and perfectly in step, so the beam stays tight and intense.
What are lasers used for?
Everything from barcode scanners and DVD players to surgery, cutting metal, and fiber-optic internet.
Part of the guide: Everyday Science: Light, Heat & Matter →