500 Lasers Are Not Necessarily Better Than One, But They Look Great

If playing with but a single laser pointer is fun, then playing with 500 laser pointers must be 500 times the fun, right? So by extension, training 500 laser pointers on a single point must be the pinnacle of pointless mirth. And indeed it is.

When we first spotted this project, we thought for sure it was yet another case of lockdown-induced  boredom producing an over-the-top build. Mind you, we have no problem with that, but in this case, [nanoslavic] relates that this is actually a project from a few years back. It’s really as simple as it looks: 500 laser pointer modules arranged on a plate with a grid of holes in a 25 by 20 array. As he placed the laser modules on the board with a glob of hot glue, he carefully aimed each one to hit a single point about a meter and a half away.  There are also a handful of blue LEDs nestled into the array, because what project is complete without blue LEDs?

The modules are wired in concentric circuits and controlled by a simple bank of toggle switches. Alas, 500 converging 150-mW 5 mW lasers do not a 75-W 2.5 W laser make; when fully powered, the effect at the focal point is reported to be only a bit warm. But it looks incredible, especially through smoke. Throwing mirrors and lenses into the beam results in some interesting patterns, too.

You’ll still need to take safety seriously if you build something like this, of course, but this one is really just for show. If you’re really serious about doing some damage with lasers, check out the long list of inadvisable laser builds that [Styropyro] has accumulated — from a high-powered “lightsaber” to a 200-Watt laser bazooka.

(Terminate your beams carefully, folks. We don’t want anyone going blind.)

29 thoughts on “500 Lasers Are Not Necessarily Better Than One, But They Look Great

        1. It’s all about how tight the beam is. Here they’re being focused by aiming them, by hand, with hot glue.

          Which isn’t a dig on the project, because it seems to have been intended to look cool. But the tightest spot isn’t all that tight.

          But totally on the 5mW modules. What Mark said.

        2. It’s just that laser light doesn’t add linearly. There’s a random phase difference between any two emitters which is just as likely to cause destructive interference and cancel out the energy of the beam where they cross.

          1. Whenever there is destructive interference there is corresponding constructive interference somewhere else, the energy is ending up in these constructive regions which lowers the concentration at any particular point.

          2. Ever noticed that a laser spot looks very noisy to the eye? It’s because you see the peaks and troughs of the interference after scattering on the surface. If you’d take the Fourier transform of that pattern you could analyze properties of the thing you’re shining at.

            Just adding two laser beams is just like adding noise to noise. It makes the peaks twice as bright, troughs are still 0 and the average is doubled. It has to because of conservation of energy, like Gary says.

          3. The energy is still there – it just won’t all go to the exact same spot at the exact same time. The phase differences and the constructive and destructive interference between multiple emitters causes the energy output to diffuse over space, so you can’t focus it as tightly as you could a single coherent emitter.

            A simpler way to understand it is that multiple lasers combined act like a regular light source – the combination of the beams is not coherent.

  1. Please don’t promote StyroPyro as a source of good ideas. The kid takes nobody’s safety into consideration, and the paramedics that come to resuscitate him stand serious risk of being electrocuted themselves, if first he doesen’t end up seriously injuring some innocent passer-by.

    1. Was thinking the same. Even just start with controls for the 7-8 switches that he’s already got. Could be very cool.

      But individually addressable + fog would be really fun.

      Heck, if you went that route, you might not even want to aim them all the same. Could have fun with random angles and see what “art” comes out in the programming.

  2. Eh?
    I’ve watched most of his videos and he’s very focused on safety.
    It’s really hard to do stuff he does and make it look dangerous but be safe.
    Please , if I’ve missed stuff give me some examples so I can apologize and eat my hat.

    1. An imperial crap tonne of beam splitters, polarisers, and lenses could put you on the road to some expensive disappointment, but the military vehicle you’ll need to mount it on would be cool.
      Growing your own giant ruby crystal might be more efficient. But you won’t get that “Death Star” appeal with the single beam.

  3. Since light is alternating EM field shouldn’t the saves need to be aligned both in polarization and period to be amplified?
    Although lasers are only emitting a single polarization, the polarizations between lasers would also need to be aligned.

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