I read laser beams get wider, like a few feet wide by the time they hit the moon, Is that a manufacturing limit, or just something about the physics of laser light? Is a perfect laser beam that doesn’t get wider possible?

Question

I read laser beams get wider, like a few feet wide by the time they hit the moon, Is that a manufacturing limit, or just something about the physics of laser light? Is a perfect laser beam that doesn’t get wider possible?

In: 5280

Answer 1

Any beam of light will end spreading out as a spherical wave. Any beam of electromagnetic radiation, as a matter of fact.

Close to the emitter, a laser beam can be modeled as a perfectly cylindrical beam, without any divergence. That’s what’s called the [near field condition](https://en.wikipedia.org/wiki/Near_and_far_field). However, farther away it will start behaving like any other source of light. That’s the far field.