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Thread: Combining two 473nm beams into one

  1. #1
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    Default Combining two 473nm beams into one

    I've got two 100mw 473nm lasers (identical). I want to combine them to increase the output. What would the optics look like to do that? A prism?

  2. #2
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    Lightbulb

    You actually use a cube, polorized beam splitting cube, and shoot the lasers in the opposite direction from where the one would go if you were splitting it. But the lasers have to be polorized and they must be opposite polorization from each other... or you rotate one, but you get my point. I am not sure the CNIs are polorized correctly. I am not sure it they have to be 1:1 or 100:1... I am not that up on the physics, I am regurgitating what others have said. I do know you use a PBS Cube.
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    Quote Originally Posted by allthatwhichis View Post
    You actually use a cube, polorized beam splitting cube, and shoot the lasers in the opposite direction from where the one would go if you were splitting it. But the lasers have to be polorized and they must be opposite polorization from each other... or you rotate one, but you get my point. I am not sure the CNIs are polorized correctly. I am not sure it they have to be 1:1 or 100:1... I am not that up on the physics, I am regurgitating what others have said. I do know you use a PBS Cube.
    Ohh don't worry there are tons of polarizing optics out there.
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    Quote Originally Posted by Dr Laser View Post
    Ohh don't worry there are tons of polarizing optics out there.
    So, is there a cube with polarizing filters out there? Where? Can you link me an example? I'm so new to this all I don't know where to get stuff. I know Edmunds sells optics. That's about it.

  5. #5
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    Lightbulb

    No, there is a cube that combines polarized beams and there are filters to polarize beams... (I am hoping someone else will take over from here...)

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    Quote Originally Posted by allthatwhichis View Post
    No, there is a cube that combines polarized beams and there are filters to polarize beams... (I am hoping someone else will take over from here...)
    So, I need a cube AND a set of polarizers for each laser so i can rotate the polarity 90 degrees so that both beams won't create an interference pattern correct? (digs deep into college textbooks).

    QUESTION #1) Doing all this is going to introduce losses. Is this worth it? I have two 473 lasers operating at about 80mw each. Should I bother?

  7. #7
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    Yes there will be losses but these will be minimise dif you use a cube thats ar coated for blue - like the laserwave types
    I have a CNI blue that is polarised enough to work with a cube and im sure they will all be the same. So I would buy a cube and try it if it dont work then you can look at polarisng optics.

    One neat side effect of combining 2 blues is that the noise on the beam - jellybeans - will occur at different points so the overall scan should look smoother than with just one laser.

    Rob
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  8. #8
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    its simply called a polarizing beam splitting cube. you need to know the polarization of each laser beam (horizontal Vs. Vertical.)

    and project them 180 deg out of phase of each other through the PBS. this will combine the powers of both beams so that you have double power out. (minus the loss through the optics obviously).

    search through here for PBS cubes and combining beams. Adam has a great explanation (as do many others) of how this works. Much more technical than my explanation.

    -Marc
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    Cool

    Quote Originally Posted by FrankenPC View Post
    So, I need a cube AND a set of polarizers for each laser so i can rotate the polarity 90 degrees so that both beams won't create an interference pattern correct? (digs deep into college textbooks).
    No, not quite. If your lasers are not polarized already, then installing polarizing filters in front of them will introduce significant power loss - to the point that the whole project would be pointless.

    However, many DPSS lasers *are* polarized, so you have a pretty good shot at it. Find out the polarization ratio of the lasers, and if they're 50:1 or better you are in business.

    You'll still need a polarizing beam-splitting cube though. (This is a cube that is designed to split a randomly-polarized beam of light into it's horizontally polarized and vertically polarized components. We reverse the process to mix a pair of beams to get a more powerful output beam.) I think LaserWave sells them for around $35...

    You mount one laser so it's output is horizontally polarized, and the other so it's output is vertically polarized. (Yeah, this may involve some complex mounts!) One beam goes straight through the cube, while the other enters the cube from the side and reflects off the polarizing filter mounted diagonally inside the cube, merging with the first beam. (See the picture that Marc posted above.)
    QUESTION #1) Doing all this is going to introduce losses. Is this worth it? I have two 473 lasers operating at about 80mw each. Should I bother?
    It's worth it so long as you're only talking about the losses through the cube, which will be just a few percent tops for each laser. So with a pair of 80 mw lasers, you could expect to get 150 mw of output (maybe slightly more), assuming you have something close to 100:1 polarization ratio (a common figure) on the lasers and you buy a PBS cube that's spec'd for blue wavelengths.

    Adam

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    Quote Originally Posted by buffo View Post
    No, not quite. If your lasers are not polarized already, then installing polarizing filters in front of them will introduce significant power loss - to the point that the whole project would be pointless.

    However, many DPSS lasers *are* polarized, so you have a pretty good shot at it. Find out the polarization ratio of the lasers, and if they're 50:1 or better you are in business.

    You'll still need a polarizing beam-splitting cube though. (This is a cube that is designed to split a randomly-polarized beam of light into it's horizontally polarized and vertically polarized components. We reverse the process to mix a pair of beams to get a more powerful output beam.) I think LaserWave sells them for around $35...

    You mount one laser so it's output is horizontally polarized, and the other so it's output is vertically polarized. (Yeah, this may involve some complex mounts!) One beam goes straight through the cube, while the other enters the cube from the side and reflects off the polarizing filter mounted diagonally inside the cube, merging with the first beam. (See the picture that Marc posted above.)

    It's worth it so long as you're only talking about the losses through the cube, which will be just a few percent tops for each laser. So with a pair of 80 mw lasers, you could expect to get 150 mw of output (maybe slightly more), assuming you have something close to 100:1 polarization ratio (a common figure) on the lasers and you buy a PBS cube that's spec'd for blue wavelengths.

    Adam
    Wow, for 35$ it's worth it to test. Doubling 473 power is an expensive proposition with a single laser! Thanks for the great info!

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