We can't tell you what might be scaled down, because those technologies don't exist, and likely never will. At least not as personal weapons.


In the world of [insert world name here], lasers became very important, because reasons and we need to scale down lasers as much as possible, while still retaining around 8kW power output for rifles and pistols.

These lasers are mostly free-electron lasers, their structure is 100% match to the IRL versions, we need to scale down these structures to versions, that can be carried around by ordinary humans.

  • I don't care about financial issues I have infinite cash.

  • Energy is not a problem.

  • The weapon should kill the target and only the target.

  • I have nanobots (with the size of a tardigrade) at my disposal to build things up from the molecular level.

What tricks can I utilize to scale down the size of various components of this laser type, if it's possible?

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    $\begingroup$ Saying "energy is not a problem" is just another way of saying "the biggest problem is not a problem". The difficulty of scaling down laser weapons is all about getting sufficient energy into them. $\endgroup$ – Mike Scott Mar 25 '17 at 17:24
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    $\begingroup$ Your 'objections' proof nothing. They're weaker then a .22 subsonic. Completely useless for any form of combat. If you can fix the power you should be able to just scale down everything, you're at that tech level. $\endgroup$ – Mormacil Mar 25 '17 at 19:43
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    $\begingroup$ High energy output also requires a way to dissipate heat - you just can't generate and use high energy without heat building up in the weapon. That's a real problem. I'd also agree that ignoring the basics of power production is tantamount to saying "magic". Worrying about details like how to scale down components when you're using a magic wand seems a bit silly. $\endgroup$ – StephenG Mar 25 '17 at 21:20
  • $\begingroup$ @StephenG Sounds like a good justification for this trope $\endgroup$ – Mephistopheles Mar 25 '17 at 21:42

The key is first shrinking the particle accelerator down by several orders of magnitude. Once you have the electron beam you can “undulate” it.

The SLAC public lecture series has a video on exactly this — “Particle Accelerator on a Chip” that explains how the microwave resonators used in accelerators could be shrunk by moving to optical freqiencies, and the whole thing fabricated using current semiconductor wafer technology.

Note that these are the same people who have a X-ray laser, so other videos on that playlist include details of just how the free-electron laser works.

Another promising approach is a tecnique called plasma wakefield acceleration.

Either approach will allow scaling down a powerful linear accelerator of electrons from miles down to bench sized.


The main (remaining) problem seems to be the driving electrons. You need a particle accelerator here. You cannot use a linear one, since it will be many hundred meters long. Therefore you will use a small, circular accelerator. But to remain on a 10cm radius circular trajectory, while approaching lightspeed, electrons have to have extreme centripetal acceleration.

Thus you would have to include extreme magnets. Even if you solve it by superconductors, and manage to handle the side effects of the extreme magnetic field on the user, there is a more fundamental problem: accelerating charges radiate.

An electron is such a small particle accelerator would very quickly loose energy in the form of synchrotron radiation. Even if you manage to pump more energy in it, than it looses, it will radiate in all directions, thus destroying your third requirement. (only the terget)

  • $\begingroup$ Can I solve some these problems with this? $\endgroup$ – Mephistopheles Mar 26 '17 at 8:53
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    $\begingroup$ @RedactedRedacted I don’t think that will help. But, see my answer: you can use a linear one, shrunk down to meter size. $\endgroup$ – JDługosz Mar 26 '17 at 9:13
  • $\begingroup$ Looks like JDługosz have right. The 'magnetic wormhole' might help you with safer control magnets, but cannot override the basic laws of physics. But if (as in his answer) you use a linear accelerator, you have at least a chance. (However, his citation uses lasers to drive te accelerator. It seems to me inefficient to use a laser to power an accelerator, which is used to power the laser.) $\endgroup$ – b.Lorenz Mar 26 '17 at 10:18
  • $\begingroup$ Powering a laser or powering microwave emitters—same difference, just different frequency. You need power to generate the field used to accelerate. $\endgroup$ – JDługosz Mar 26 '17 at 23:49
  • $\begingroup$ @JDługosz Yes, but since we want a laser weapon, not a microwave one, we could simple fire the original high power lasers on the enemy. The gun gets lighter, and some of the losses fall out . $\endgroup$ – b.Lorenz Mar 27 '17 at 13:14

I like the answers because people are thinking. I propose a study of nature if power is no object. The light source could be bio-luminescent as both bacteria and bio-chemical reactions can produce light. Look to the scales of a butterfly wing to tune and possibly direct your beam. it may not be fancy but it may do the trick


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