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Thread: Interesting Reddit Question about Lasers

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    Default Interesting Reddit Question about Lasers

    "Can two lazers that both emit light outside of the visible spectrum interfere with each other to create a visible pixel at their intersection?"
    http://www.reddit.com/r/askscience/c...ht_outside_of/
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    As a general rule I don't answer questions where Laser is spelled with a Z.

    That said, there have been several materials used for 3D display at the intersection of two different wavelength laser beams. Mercury Vapor and Two Photon Upconversion crystals come to mind. A pretty lady research person came to the ILDA Meeting a decade or so ago with a upconversion demo , where two tuned IR lasers were fed into a grown crystal (probably a doped soft glass) at right angles, via galvo pairs. Where they intercepted was a glowing pinkish white spot in the crystal. She left with what she wanted, funding for more research. Hanging off her arm was a wealthy laserist. He probably got more trouble then he wanted... But all of us were chasing her, smart, beautiful, and with one heck of a potential product. I do know there was a startup... I was scared of the crystal, she didn't have blocking filters on the faces and there were many watts of diverging IR floating around.

    Short version, unless there is a active material where the beams intersect, almost nothing happens even with very high power beams. If you have such a material, Its not a very efficient process either, except for frequency doubling. The threshold energy is usually more power then your average hobbyist can obtain. I service such systems every once in a while...

    The Reddit guys disappoint me, in the 200 posts I read, many of them got very close but no one hit the unified physics answer on how to do it. .....
    A few got really close. Some got the theory but few got anywhere near the hardware answer. I shouldn't dog on them too much, not too many people get beyond the text book on non-linear optics and spectroscopy. If they would have Googled.....

    Ah, I see "xnormal" and "VodkaDip" got it right....

    Steve
    Last edited by mixedgas; 07-09-2014 at 17:03.
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    Quote Originally Posted by mixedgas View Post
    As a general rule I don't answer questions where Laser is spelled with a Z.

    That said, there have been several materials used for 3D display at the intersection of two different wavelength laser beams. Mercury Vapor and Two Photon Upconversion crystals come to mind. A pretty lady postdoctoral person came to ILDA a few decade or so ago with a upconversion demo , where two tuned IR lasers were fed into a grown crystal (probably a doped soft glass) at right angles, via galvo pairs. Where they intercepted was a glowing pinkish white spot in the crystal. She left with what she wanted, funding for more research. Hanging off her arm was a wealthy laserist. He probably got more trouble then he wanted... But all of us were chasing her, smart, beautiful, and with one heck of a potential product. I do know there was a startup...

    Short version, unless there is a active material where the beams intersect, almost nothing happens even with very high power beams.

    The Reddit guys disappoint me, in the 200 posts I read, many of them got very close but no one hit the unified physics answer on how to do it. .....
    A few got really close. Some got the theory but few got anywhere near the hardware answer. I shouldn't dog on them too much, not too many people get beyond the text book on non-linear optics and spectroscopy.

    Steve
    Perhaps enlighten reddit with your knowledge? I'm sure your practical experience will be better than someone who knows "Strong Force | Quark-Gluon Plasma | Particle Jets"
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    And have to disclose what I work on to prove it? No thanks... One forum addiction is enough...


    Tell the Reddit guys to look at Two Photon Upconversion , Third Order susceptibility Tensors in Non Linear Optics, Optical Parametric Conversion, and read Amon Yariv's book. That should get them started. Then cite:

    "Second harmonic generation and two-photon luminescence upconversion in glasses doped with ZnSe nanocrystalline quantum dots" By Napoleon Thantu.
    Which is Journal of Luminesce Volume 111, Issues 1–2, 1 January 2005, Pages 17–24

    Here is a nice link:

    http://www.orc.soton.ac.uk/publications/08xx/885.pdf

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    Steve
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    They got the science mostly correct in the thread on Reddit. Basically, you need an interface for sum-frequency generation to work. That point was clearly stated in the top reply (or at least it was when I read the thread yesterday.) Reddit usually gets most things right.

    However, I agree that it made me cringe to see someone spell it "lazer". Ugh!

    Adam

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    Quote Originally Posted by buffo View Post
    However, I agree that it made me cringe to see someone spell it "lazer". Ugh!
    Adam
    That's a new kind of device -- Light Amplification by the Zapping of Electrons into Radiation .. right ? I think I reddit somewhere ..

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