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Thread: PBS blues.....

  1. #1
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    Default PBS blues.....

    Just curious -

    Does anyone know if a 100mw 473 nm CNI and a 100 or 150mw 473nm LaserWave could be combined with a PBS cube, and if so, how would the LaserWave need to be mounted? (I'm assuming rotated along the long axis, 90 degrees to the CNI, but assuming usually gets me in trouble...)

    Thanks!
    RR

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    You can test the polarity using the cube and rotating it in the beam of each laser to see where the axis is on each laser. Going to be tough to mount....
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    Yeah, kind of what I figured;

    I guess I'll be better off waiting for the inexpensive MechEng 473nm 250mw special
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
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    Ive seen alot of people talking about the polarity of the lasers. What is the problem with just combining them however you want? After it is just light, if you get it aligned right, it stays together? Or am I completely missing something?

    Cheers

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    the traditional way if you do not have a milling machine to make the platform to raise the laser is a bounce off two mirrors on mm1s to raise the height of one beam. If you use dielectric mirrors the loss is only microwatts. If you fold the beam straight up with a mirror at 45' the polarization rotates, so you do it diagonally. Ie go backwards toward the laser and to the left then forward towards the scanners and to the right. That reduces the polarization rotation to a minimum.

    Steve
    Last edited by mixedgas; 11-26-2008 at 19:32.

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    Quote Originally Posted by Things View Post
    Ive seen alot of people talking about the polarity of the lasers. What is the problem with just combining them however you want? After it is just light, if you get it aligned right, it stays together? Or am I completely missing something?

    Cheers
    Youre completely missing something... youre statement 'it is just light' is correct. It is just light, but its polarized in a certain way. When you combine two similarly polarized beams you are going to cancel some of the light out, and you will end up with a power much less than two beams polarized at 90 degrees to one another would.

    In a perfect world if you didn't have them turned 90 degrees to one another you would end up cancelling out any light.

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    How would laser light just "disappear" though? What I don't get, is why it has to be angled, and how light can cancel out light. I guess ive got abit of reading to do

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    Think it like slatted window blinds with a 50/50 ratio. If you have one horizontal and the other vertical you will not be able to see through. If you match the orientation then light will pass. This is polarization.
    On a cube combiner the cube will reflect light in one polarization and pass in the other. If you have one laser vertically polarized and the other horizontally if you put the cube in the right plate you can overlay the two beams on each other then they become 'randomlly' polarized.

    Pretend that the arrow is facing the other direction.

    chad
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    Hi Stuka,
    Chad pictures show the perfect using of PBS.
    just let the light pass the PBS, if one laser reflection and the other transimission the pBS, you are lucky, that's meaning the 2 lasers had different polarization, you no need rotation 90 degree for combine. if both are transimission or reflection, you need change one 90 degree for combine them.
    Best regards!
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  10. #10
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    Quote Originally Posted by Things View Post
    How would laser light just "disappear" though? What I don't get, is why it has to be angled, and how light can cancel out light. I guess ive got abit of reading to do
    None of it disappears, due to conservation of energy. Light that does not go in the desired direction and polarization from the cube's point of view goes out the other side or gets reflected back to the laser, and a small amount gets adsorbed and turned to heat.

    BTW, simple explanations of things like interferometers say light waves cancel. In reality, they get reflected right back to the laser when interference nulls occur. BTW, light from two different green lasers WILL NOT interfere, you need "quantum entanglement" from the sources.

    Steve

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