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Thread: Change laser to non laser

  1. #1
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    Default Change laser to non laser

    I want to mess with optical links. One problem is mode hoping and the other is scintillating. Can you for lack of a better word homogenize a laser back normal light to eliminate these features but still retain to any degree the beam. I still have to telescope 20x anyway to make a large enough beam to use. The only reason to use the laser is density. Not sure yet if polarization is good or bad or doesn't matter. Want to try 150km link. Might want to use a laser embedded with a sync pulse for alignment.

  2. #2
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    I'm confused... Do you need to spoil the spacial coherence? Because that should happen automatically after a few meters of propagation, no?

    Have you tried up-collimating the beam through a reverse telescope and just firing it off towards yonder mountain-top receiver to see what you get? Are the scintillation issues related to speckle (in other words, interference based)?

    I'm thinking that any monochromatic source will eventually interfere with itself due to frequency coherence, unless you pass the beam through a fluorescent medium or something. (Like the Ca$io slim green projectors did to generate green from the array of 445 nm blue diodes, for example...) Though I doubt the beam quality would be very good after that.

    Adam

  3. #3
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    The scintillation causes noise on a long distance path but laser is very directional so it keeps the signal power up. If I can keep the divergence of the laser and loose themode hoping and scintillation that would be ideal. Still expanding beam about 20x. I want a beam that is a good 6-10' across at 100 miles. I am thinking to use something as a beacon and then lock in on a tighter beam. It's just for fun. Mountain to mountain.

  4. #4
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    I have a thought based on yours. Receive the signal then focus the beam with a lens onto a frosted surface with the dectector below. The should average the beam. I'm using pwm so on and off only count.

  5. #5
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    Brilliant! I was thinking about changes at the source. But of course, spoiling any coherence-related interference at the destination is far more reasonable. Some frosted glass would probably work nicely.

    Please post back here when you've had a chance to test it. Genuinely curious as to how this works... (Or better yet, come to SELEM and we'll chat about it in person!)

    Adam

  6. #6
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    ... I'm using 105Ám glass-fibers to "homogenize" laser beams - could be worth to test with collimating at 20x output beam diameter, to check the resulting divergence ...

    Viktor

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