Question about increasing laser power

[Josiah]

TL;DR

Would this work?

Hi, Im not sure if this is the right forum to post this question. If you had a laser, then reflected it back on its self, and then reflected it back again, would this enable a super high powered laser? Because it would be continuously reflecting back on it self at the speed of light.

 

[.Scott]

There are two kinds of lasers, continuous wave (CW) and pulse. Since you're thinking of CW, that is what I will address.

Most CW lasers work by reflecting light back and forth between two mirrors. A certain amount of energy is pumped into that system and that results in a monochromatic beam that (within some degree of precision) is in-phase with itself. One of the two mirrors will be only partially silvered (or in certain cases, missing) and so a portion of the laser beam crosses to the exterior and is available for use.

If both mirrors are 100% reflective, then you might think that the more energy you pump in, the more that would accumulate in the laser in the form of a steadily power-increasing laser beam. To some extent, this is true. But what will happen is that the elements responsible for pumping energy into the beam (the ionized gas, crystal, or semiconductor) will reach a limit where they are absorbing as much energy as they are pumping into the laser beam.

At that point, the laser beam will remain at that power limit (or possibly begin reducing) as the equipment uses the remaining energy to produce heat.

 

[FactChecker]

I believe that is how they work, up to a certain power (20W?). Trying to do that too much starts to melt parts. I am just a casual amateur, but here is an interesting YouTube video: I Built an Insane 260W LASER That Cuts Metal !
Of course, the military ones probably are a different thing entirely.

ADDED: A lot of the video comments say how crazy reckless it was. I'll leave this stuff to the experts and the nuts, and just enjoy the YouTube videos.

 

[Roberto Pavani]

up to a certain power (20W?)

The answers above are correct. Just adding a safety note: any laser above ~500 mW (Class 4) requires proper eye protection, not just from the direct beam, but from diffuse reflections off walls, dust scattering, and
secondary reflections from ordinary surfaces. At 260W, scattered light alone can cause permanent eye damage.

 

[DaveE]

TL;DR: Would this work?

Hi, Im not sure if this is the right forum to post this question. If you had a laser, then reflected it back on its self, and then reflected it back again, would this enable a super high powered laser? Because it would be continuously reflecting back on it self at the speed of light.

Virtually all lasers use this, or similar, techniques internally to function optimally. You won't make their design better by adding your own. In practice, retroreflections can cause significant problems in performance and reliability for lasers.