Stimulated emission

[upbeat music] A photon can pass by one of those excited particles and cause it to release another photon that matches it.

That process is called stimulated emission.

The new light can match the first light very closely in color and in the way its light waves are moving.

Then those photons can cause more matching photons to be released.

One of those mirrors allows some of the light to escape, and that escaping light is the laser beam.

That's also where the name laser comes from.

The letters stand for light amplification by stimulated emission of radiation.

The device is basically using stimulated emission to make more and more organized light.