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My question is: Is it possible to make laser beams viable midair without smoke? I thought it would be a great idea to have a (second) smartphone or pc screen without having a solid screen. The reason why it has to be without smoke is that smoke would be too dependent on the environment.

If it is possible to make laser beams appear in some way midair (without smoke, just air), would this be possible? I am not sure if its possible with two lasers "collide" or some other way.

Wouter

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  • $\begingroup$ Since ultimately you want a screen-like display, not just a visible laser, I'll only leave this as a comment. Even in clean air a visible laser (green works well) will backscatter off particles, making the beam visible particularly from behind. I use a 35 mW green laser for astronomy demonstrations all the time. At night the beam can be seen hundreds of feet into the air. At the same time it's worth pointing out that, as cool as they are, lasers are not always the best technology for the job. $\endgroup$
    – user10851
    Nov 24, 2014 at 14:50
  • $\begingroup$ I think if you threw flour or any powdery substance in the air it could show the lasers as they could reflect of those pieces in the air. $\endgroup$
    – I_Draco
    Apr 5, 2017 at 19:34

3 Answers 3

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It is possible to hit spots in the air with laser pulses from multiple directions in such a way that air molecules in that spot become ionized and emit light, see the technology discussed in this article, along with this demonstration video.

And if you just want a 2D screen rather than a 3D display, then of course you can also just use lasers to project it on a surface, like the "laser projection virtual keyboard" here.

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    $\begingroup$ The only limitation of this technology to me seems to be that it does not allow for multiple colors. I am not an expect on plasma emission, so maybe it might be possible to achieve different colors. Either way this is some interesting technology. $\endgroup$
    – fibonatic
    Nov 23, 2014 at 23:59
  • $\begingroup$ Multiple direction's aren't needed, you simply need light intense enough. Also the colors emitted by plasma in the visible range correspond the the electronic structure of the material. For gases, this is likely only gives you a few options and little control. Of course the pico/nanosecond laser system that takes up half a room is likely the bigger hurdle. $\endgroup$ Nov 24, 2014 at 3:05
  • $\begingroup$ @Godric Seer - If you didn't have multiple pulses converging, how would you make it so the ionization would occur at some distance from the laser, as opposed to right at the opening where the laser first hits the air? $\endgroup$
    – Hypnosifl
    Nov 24, 2014 at 3:31
  • $\begingroup$ You can do it with a single pulse and a lens. Just focus a single pulse down and eventually it will break down. It may even be possible to make a line with a long enough focal length. Of course there are limits to this, but it is a simpler setup that multiple beams arriving at the same time. $\endgroup$ Nov 24, 2014 at 3:35
  • $\begingroup$ @GodricSeer the problem is that long line (cone in fact) is the most likely result if you want to project far enough (like to the center of a large hall) and still have not too big aperture of your device. $\endgroup$
    – Ruslan
    Nov 24, 2014 at 16:47
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Not really; you need to have the laser light pass through particles in a medium. Laser light is made of photons; in order to see the laser, photons must be reflected off of a something to your eyes. You cannot otherwise "see" a photon because photons don't interact via the electromagnetic force - in other words, photons don't emit photons. To see the laser beam, you have to see photons reflected off of something, and so you have to have it passing through some medium for this to work. Smoke works well, as does anything that's thick and fills the air. Normal air does not work well. So technically you could use something besides smoke, but you need to have the beam pass through some medium.

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    $\begingroup$ Glass works well for holograms, and dust motes make lasers visible in air if the laser is high-powered enough. $\endgroup$
    – CoilKid
    Nov 23, 2014 at 23:44
  • $\begingroup$ @CoilKid I assumed that the laser was passing through some liquid/gas, so I hadn't considered glass. I did think about dust motes, but I figured that they would count as "air" in this case. $\endgroup$
    – HDE 226868
    Nov 23, 2014 at 23:56
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I recently saw a video of a demonstration by a Japanese researcher who came up with a method that used a pair of high-powered (presumably) infrared laser beams that, where they intersected, heated the air enough to turn it into plasma, creating a pulse of white light. It works, but it's slow, low-resolution, & requires staggering amounts of power. If you come up with a better method that actually works, don't tell anybody about it until you've patented it. :)

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  • $\begingroup$ More information and a link would be nice. $\endgroup$ Nov 24, 2014 at 8:05
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    $\begingroup$ Aerial Burton $\endgroup$
    – jasper
    Nov 24, 2014 at 9:46
  • $\begingroup$ Wouldn't that also heat up the whole room by design? $\endgroup$
    – ASA
    Nov 24, 2014 at 12:03

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