Laser beams range in power from a few microwatts to several billion watts in short bursts. How a Laser Works To understand how a laser works, first you have to understand something about light. Light is the visible form of electromagnetic energy. Some electromagnetic energy cannot be seen, but it is everywhere in the universe. It is made of tiny energy packets, called photons, traveling in a stream of wave patterns, called electromagnetic waves.
All objects emit electromagnetic energy in varying wavelengths and directions.
Photons are emitted when atoms spontaneously change from one energy state to another. We can feel some of them as heat, and we can see others as light. But even when we can't see or feel them, photons are moving all around us in different directions, getting absorbed by atoms and released again. In a laser, however, the photons are emitted in the same general wavelength and direction. It was Albert Einstein who first conceived of laser light.