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

Hi.
To answer very briefly: It is about the physics of light (or waves in general).
Even if you have a perfect laser, it will always diverge. As do waves on water when you drop something into it. But you can decrease this divergence by making your laser beam larger or by making the color more “blue” than “red”.

Details:
It doesnt matter what is your starting point really. You can start with a small laser pointer for instance. Then you tak two lenses. One lens that will make the beam more divergent and the other which will focus it. If you place them at a correct distance from each other, you will obtain a larger laser beam which will be much less divergent than the laser pointer output. We call these two lenses a “telescope” and the laser beam that diverges very little is called a “collimated” beam.
Also, longer wavelengths diverge more, but to explain this I would really have to talk some math.

Source: PhD in laser physics