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Combining multiple laser beams (same wavelength)

jors

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Hi all!
Want to build high power rgb laser.
I've find several ways to combining multiple beams, say, knife edge & beam splitter techniques (once).

but... for example please take a look at KVANT 30w rgb:
http://p.globalsources.com/IMAGES/PDT/SPEC/785/K1072773785.pdf

How they obtain, for instance, 10W/445nm?? knife edge here?
Awesome20Laser20-2020wattstechnics_.jpg Photo by magicmushrooms1 | Photobucket

the same for Red module: 10W/637+660nm etc

Any ideas about technique they use?

Many thanks!!

Jordi
 

upaa27

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Using 2 dicros you should be able to do it. Just fire red and blue through one and the beam that comes out, let it go into the second dicro and then fire the green.
 

Cyparagon

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You missed the part where he said same wavelength^

Yes, OP. Knife edge to combine 24 diodes, followed by beam contracting telescope, followed by PBS cube to combine it with the other 24 diode array.
 
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Knife edging, PBS cube, and dicros are the 3 methods of combining beams, a dicro combines 2 beams of different WL, you can buy one for most any pair you want and they are usually expensive. A PBS cube can only combine 2 beams once and the result can't again be combined through another PBS cube. Knife edging can combine several beams at once that can then be combined with other beams though a PBS or dicro, so its not uncommon to combine 2 of these methods or maybe even all 3 to achieve your desired result.

Alan
 

upaa27

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You missed the part where he said same wavelength^

Yes, OP. Knife edge to combine 24 diodes, followed by beam contracting telescope, followed by PBS cube to combine it with the other 24 diode array.
Sorry about that ^^. For combining just 2 beams of the same wavelength a polarizing beam splitter(PBS) is your best bet as they knit the beams together instead of bringing them really close. For more than that I would say knife edging is best.
 

jeffwebb

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I have been working on a few other ways to combine multiple laser beams with the same wavelength. My goal is to make it simple so anybody with a few extra laser diodes laying around can make a more powerful laser. :eg:

I had this idea a few years ago, but I did not do anything with it. The concept is to take advantage of Total Internal Reflection. When a light source coming from a denser medium such as quartz hits the boundary with a less dense medium such as air past the Critical Angle all the light will be reflected. At the point of TIR additional laser can be added and they will be axially aligned. The sides of the optic will be AR coated so light loss will be minimal when adding lasers.


Example 1: Waveguide Approach


https://drive.google.com/file/d/0BwvDRdFmhRNYQ1RtS2NBOG9jcFU/view?usp=sharing

Example 2: Virtuous Circle Approach


https://drive.google.com/file/d/0BwvDRdFmhRNYX1lQeFVHRmxnWmM/view?usp=sharing



The closer to the edge of the cylinder the more sides and the more lasers can be added. I have some concern that a cylindrical shape on the internal reflection point may mess up the alignment of the laser after a few reflections so this may need to be a multi-sided shape.

Example 3: Hex My Ex Approach


https://drive.google.com/file/d/0BwvDRdFmhRNYbHpfVlpKekNUSk0/view?usp=sharing

Now how many laser diodes can one add; well that is limited to the initial laser not adding any additional photons, depending in the precision of the laser system, but I can see people making a kW level lasers with this method. I currently have five 2W laser diodes combined because that is all the diodes I had laying around. I am working on creating a loop with these elements so I can pump the laser diodes. :shhh:


Happy Lasing,
Jeff Webb
 

Alaskan

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Is the advantage being able to combine beams one on top of the other like a PBS cube does, except without regard to polarity? Otherwise, a knife edge is far smaller but then the beams are placed side by side and from that, a wider output.

OMG, I was sucked into a very old thread but I am interested in Jeff's diagrams as possible alternative methods, are they viable?
 
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jors

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I'm afraid those setups don't work: If internal sides are TOTAL REFLECTION, is not possible to fire a beam thru them from outside...although angles.
 
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RedCowboy

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It would have to pass through from the outside yet reflect on the inside and an exit hole would have to be made, but I don't think quartz will do this
 

CDBEAM777

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It would have to pass through from the outside yet reflect on the inside and an exit hole would have to be made, but I don't think quartz will do this

One projector from China used this method...See attached pic !!

But......No other projector company uses this method !!!

SOoooo....that means that either " Laser King " ( Special beam combining method) is way ahead of the pac........or there is a reason why this method is not used !!!

I suspect high optical loses...or critical angle position requirements !!! or an issue with maintaining critical angle positioning !!!

Dunno ???? But...there is likely some " Fly in the Ointment " issue !!!!

Of course....God only knows what research is going on or that has occurred that has not...or will not filter down to our level !! ~Fairly dark down here !!:beer::beer::beer:
 

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jeffwebb

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Hey everybody thanks for the feedback. I really appreciate everyone’s’ thoughts. Please keep it coming!!!

Let me clarify what I am trying to do. I am taking advantage of the Total Internal Reflection a concept when a light source comes from a denser transparent medium to a less dense transparent medium will reflect not transmit at an angle greater than the Critical Angle. We can use Snell’s Law to calculate the Critical Angle/Angle of Incidence.

Check the 1:14 mark of this video.
https://www.youtube.com/watch?v=mtVbb_MWNDg

When I was in school I sat through a similar demonstration but it was not a few years later I if figured there may be a way to add lasers at the reflection points.

If we replaced the water with say a better optical medium such as crown glass we can create the same wave effect. Since the medium is transparent we can add laser at the reflection points. If we coat the transparent medium with an anti-reflective coating preferably one that is tuned to the wavelength of the laser we will not lose much light from the added laser. Since the subsequent laser sources are coming from a less dense medium into the denser medium TIR does not occur.

I did an experiment a few years ago with acrylic and I was able to align a few laser beams. It was extruded acrylic so it was optically terrible. I did not continue because life got in the way. Anyhow I have some AR coated windows coming from Edmund's Optics; I have a few other projects I am working on so stay tuned.
 

logsquared

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Unfortunately light can't be "trapped" in this way. The "waveguide" approach can't work because the beam(s) entering the side(s) will never reach TIR due to refraction as it enters the glass.
 

jeffwebb

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Ahh yes refraction is a bear. That is why in all the waveguide demonstrations have the laser entering from the side. Solve for refraction by working with it and/or create more space for the laser to work is key.

The diagram below is a waveguide example for Pyrex.

https://drive.google.com/file/d/0BwvDRdFmhRNYQ0JPS3JNUU9xQ0U/view?usp=sharing

As you can see the top and bottom angles are way too shallow in this example.
 




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