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

A perfect laser will diverge at an angle determined by just the wavelength of light and its aperture, the initial diameter of the beam. The angle is twice the wavelength divided by pi divided by the aperture. So a 10mm green laser will be at least 12km wide by the time it reaches the moon.