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Happy and excited beams of light

  1. Oct 23, 2010 #1
    As of this point. I understand the following.

    1. there is almost 90% loss when applied to a laser system. 100 watts in 10 watt beam out.

    2. when a beam is split there is also a loss, (amount unknown)

    3. if you take a 20 watt beam and (with not loss) split it in two and cross the beams. The effects to not stack as the wave is the same in both.

    if i took a beam and split it in 3 equal parts. (so that they all had 10 watts) and ran 2 of them back in to two different active medium chambers to be re-excited then cross the 3 beams red green and blue would they then stack?
    (assuming you can re-excited a beam)
  2. jcsd
  3. Oct 24, 2010 #2
    1. Ok, but it actually depends on what type of laser you are specifically talking about.
    2. Why can't you can measure the loss?
    3. What effects?

    Not sure what you mean by "stack".

    I don't understand the last question, but it sounds interesting, can you elaborate?
  4. Oct 27, 2010 #3
    my idea rather crude and lacking in knowledge is thus.
    you can use 100 mirrors to focus the sun on one tower and biol water.

    i can not take 1 beam of laser and say split it in to 3 parts then have them cross at a nexus point. they will do so. but the combined power does not stack. three ten watt beams do not make a 30 watt nexus.
    (due to the waves all being the same.) (as i understand.)
    if you take the 100 watt (red) beam split it in to three parts (i don't know how much is lost when you do this) then rerun two of the beams through different active medium chambers. (blue and green)

    Will it re excite the beams?
    Will it up the power of each beam?
    (sorry Trekkie coming up)
    will it put each of the 3 beams out of phase?
    now when you run the 3 beams through the nexus will it be accumulative?
  5. Oct 27, 2010 #4

    Andy Resnick

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    It's very difficult for me to understand what you are saying, so this may not answer your question:

    You seem to be confused about radiometry- solar concentrators operate using the principles of radiometry- and how to apply it to a laser beam.

    Laser light is very different than solar radiation: the obvious one is the spectrum. More fundamentally, they differ in terms of *coherence*.

    Sunlight is spectrally incoherent: that means when you combine beams you add *intensities*. Laser light is spectrally very coherent- you add the *fields*.

    When you combine the laser light you create interference fringes- regions of spatially varying intensity. If you split a 10 W laser beam into three, when you re-combine them (unless you are very sloppy), there will be interference fringes and the power will vary from 20 W to 0 W, depending on where you measure it. On average (if the fringes move or you move the detector around, for example), you will measure 10 W.

    For incoherent light (or mutually incoherent light from multiple sources), there are no fringes and you will always measure the same total power.

    Does that help?
  6. Oct 27, 2010 #5
    If by nexus, you mean where the three beams simply cross, then yes it does add up to 30 watts overall. Just like flashlights.

    The loss can be made to be less than 1%, it's nothing to worry about.

    No and no. Different colors are independent. The active medium is only active to one wavelength, "blue" for example (+ its harmonics). A random red beam won't generally "stimulate" (la"S"er) the blue transitions. Stimulated blue emission could be made to overlap on a red beam. In this case you'd have just that, two overlapping beams, say 5W of red, and 5W of blue, giving a beam with total power 10W and 2 wavelengths. The active medium for red may well be opaque or transparent to blue, unaware of its passing.

    If you separate a red beam in three and bring them back together, their phase will be defined, but they won't necessarily be "in phase". If they all fall on the same point on a screen, you could have interference rings. If the center of the circular pattern of rings is a maximum, you could say they are "in phase". If it is a minimum, I suppose you can say they are "out of phase" at the center, but the phase is still defined.

    Generally speaking, there is no phase relationship between different wavelengths (unless they are harmonics of each other, i.e. half, double, triple etc.)
  7. Oct 28, 2010 #6
    I will try absorb that info.

    Photon = "an elementary particle"
    as a particle it should have an atomic weight right?
    and if it has weight it has a mass.

    following this train wreck of logic. then if you had a 100 watt beam strike a surface, there would have to be a measurable "force" or impact.

    but...(catch 22)
    light is not a solid, it is a wave of energy.
    but a photon is a particle.
    Last edited: Oct 28, 2010
  8. Oct 28, 2010 #7
    Ok. I was thinking that if i could make a beam of 10 watt's and split it in 3. then with reflectors/mirrors make make it bounce around till it make a "grid" that each crossing would be 28 watts. (it wont its the same beam. same wave same harmonics (?))
    But if i could introduce a second beam. the Waffle grid would produce heat and at each crossing, would add to the (speed of, but not the total temp the water is heated) the speed of the heating. 1 candle heats X water at Y time.
    100 candles heat x water at Y time.

    sort of (to bring the water from "tap" to boil.)
  9. Nov 2, 2010 #8
    thank you for the answers.
    thank you for the reply's.
  10. Nov 3, 2010 #9


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    And thats the theory behind a "lightsail" for space travel have seen in science fiction
    but I also dont know if its actually possible ??

    anyone ?

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