🚀 go-pugleaf

In article <BwtJIE.M9v@acsu.buffalo.edu> v068qlek@ubvmsb.cc.buffalo.edu (Adam Jachniewicz) writes:
>I would like to know if there are holograms that have
>been projected in free space (rather then the type projected on mirrors).
>I also would like to know if it is possible to project two nonvisible 
>laser beams (to cross each other) and produce a dot where they intersect.
>Is there such a phenomenon? I have had no sucess with this, I think that
>either the beam is not strong enough, the wrong freq.,mode,or that such
>a phenonmenon doesn't exist.


I dont really know if there is such a thing as "free space projected holography.

What I do know, altough, is that two light beams propagating in free space
don't interact with each other; they're crossing each other as if the other
didn't exist. What happens in holography is the addition of two beams
ON A MEDIA (that is the photographic plate). The two beams stay independent
but the plate records the summation.

So, to answer to your second question, two invisible beams cannot produce a
visible point at their intersection unless some media react to the beams.
Of course, if the beams are intense enough (in the range of gigawatts),
they can litterally evaporate a dust particle that happens to be on the
path, but dont expect this kind of behavior from a He-Ne laser!

Of course, I'm speaking here for ordinary linear media, such as glass
or air. But some really weird things can happen in what we call
optical non-linear media...

I hope my explanations are clear enough.


+--------------------------------+----------------------------------------+
| Richard Van Neste              | "Enivrez-vous sans cesse! De vin,      |
| graduate student               |  de poesie ou de vertu: a votre guise. |
| Centre d'optique, photonique   |  Mais enivrez-vous!"                   |
| et laser (COPL)                |                  -- Beaudelaire        |
| Universite Laval               |                                        |
| Quebec, Canada                 | (Silly translation: "Just get drunk!") |
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