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Firstly, I'm not a physics guy. I want to try to create a 3D hologram point with lasers. As I know, if I have at least 3 lasers in the same wavelength and their beam is crossing each other at a single point then it will become visible. Here for an example:

enter image description here

But I've tried this method and it's not working for me. Is there any theoretical problem with this set up, or did I miss something in the experiment?

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    $\begingroup$ Your assumption "if I have at least 3 lasers in the same wavelength and their beam is crossing each other at a single point then it will become visible." is just not true. from what point would you consider tu see this point? why should it reflect in an ey? $\endgroup$
    – trula
    Commented Oct 3, 2022 at 16:46
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    $\begingroup$ As you can see in the picture above, I think it has to be visible. $\endgroup$
    – Korte Alma
    Commented Oct 3, 2022 at 16:50
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    $\begingroup$ Maybe the picture does not show what you think it shows. The same image appears in this article, where the only claim made about it is that light from four different colored diode lasers can be combined to make a white-looking light source that is satisfactory for indoor illumination. $\endgroup$
    – Solomon Slow
    Commented Oct 3, 2022 at 17:49

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Your assumption, that crossing lasers will make them visible, is unfortunately incorrect. I’m afraid the photo has led you astray. In order to see light, there needs to be something present to direct the light toward your eyes. In your photo, the laser beams are not simply in free, clear air. It appears that the beams are grazing along a table. Moreover, it looks like there is some kind of frosted glass cylinder that the beams are lighting up at the focus (see how the beams look far more diffuse after the cylinder, and the blue light even looks shadowed). In any case, there is plenty of scattering happening, redirecting some light to the camera. Do this experiment in vacuum, with no cylinder and no table, and you won’t see a thing. The light from the cylinder looks white because of the mixture of several colors across the spectrum, and it looks uniform on the cylinder because the camera is probably saturating.

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  • $\begingroup$ So, for example, if I put there some kind of fog, smoke something then it will be visible? $\endgroup$
    – Korte Alma
    Commented Oct 4, 2022 at 7:37
  • $\begingroup$ Yes, than it will be visible, but also the three beams. and it has nothing to do with hologram $\endgroup$
    – trula
    Commented Oct 4, 2022 at 11:06

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