Best Way to Combine 445s

I am looking to combining two A-130 diodes, into one output.

I just need some opinions on the best way to do it. I've found group buys that would allow me to use a coated PBS cube, which would give me an output in the shape of a (+).

I've also considered a perhaps cheaper option, which would be the knife edging technique. It would allow for a better beam profile that sort of looks like (=).

Which beam profile would allow for best beam specs? Low divergence would be nice, but a smaller beam diameter would also be nice. I'm just having trouble deciding since these diodes put out such a long strip instead of a round spot.

PBS? Or Knife Edge?

Would it be advantageous in either situation, to expand the beam and re-collimate it after the combination?

Knife edging, or stacking one beam on top of the other might not allow it, would it?

Also, which option can be done cheaper? I'm on a budget. I though I would use some of Drew's lab heatsinks to work as the aiXis mounts.


Thanks Everyone!

-Tyler

:anyone:

I don't believe anyone knows enough about these LD's, or the factors involved in combining them, yet. This is why you have gotten no reply's.:cryyy:
Give it some time and the answers will come.

PBS, for 99% sure ..... after all, they are polarized as any other laser diodes, so .....

PBS would be preferable for the optical result, but the question remains on how you should go about that.

I doubt there is much experience on this point so far, and pbs cubes coated for 445 will not be available at the moment. So that limits your option to using a PBS cube intended for 405 (or even red). I'm not sure how much the power loss due to that will be, but i suppose there is only one way to find out

Costwise there won't be much of a difference - to get the knife edging really right you'd probably need pricey adjustable optical mounts.

Just as hypothesis, cause i don't have a spectral analyzer ..... but, you don't think that PBS cubes like, as example, the ones in the PHR sleds, have broadband coating ? ..... after all, they work both for BR and red, and i've never noticed too much loss, using them in a sense or in another ..... so, probably they are good enough also for 445nm .....

Anyway, one thing is right, they are small ..... maybe better find some decent-sized cube for BR, for do an effective experiment .....

I decided to go the knife edge route. I have found it to be cheaper, as a cube can run $55 on it's own.

The knife edging technique will still have a weird output profile, but it will be workable since I'm looking to achieve a 'cleaner' looking dot. Think of what the diverging fast axis will make the output look like after 50 ft! It would be a huge + with one of the diodes rotated for PBS cube passage.

If I found a lens with a short focal length, and then mounted a 405-G1 after the beams crossed, I think I could gain back, a small beam diameter. It would kill my divergence, but does anyone think it would be worth trying?

If you can keep the two "oval shaped" beams with fast axis parallels, you can end with a better beam shape, at the end ..... also, doing a "pre-focusing" of the beams, combining them on the mirror, then using a final lens for focusing, can give you a better divergence (but, ofcourse, with an initial "fat" beam)

Excuse my ignorance, but what is this "knife edging" beam combining technique? I've tried looking it up, but can't find a good explanation.

Andy has a great picture here that might help the description.



You just reflect two beam into a parallel direction. The beam on the beam ends up, JUST scraping the edge of the second mirror. This gives a nearly un-noticeable transition from one "dot" to the other. You basically get two dots right next to each other. Pretty much touching. Hopefully this is a good enough explanation..

Please excuse the large picture size..

Meatball said:

Andy has a great picture here that might help the description.

Click to expand...

Dang, I can't see that since I don't have a PL account. However, I've seen pictures of it, but didn't know what it was really depicting.

You just reflect two beam into a parallel direction. The beam on the beam ends up, JUST scraping the edge of the second mirror. This gives a nearly un-noticeable transition from one "dot" to the other. You basically get two dots right next to each other. Pretty much touching. Hopefully this is a good enough explanation..

Click to expand...

No, that's a good explanation. It does mean you get a fatter "beam" from the combination right?

You get a fatter beam from the start - in fact it will look something like TEM01 since the most intensity is in the middle of each beam, and they touch on the edges. At some distance the divergence of each beam will cause the resulting dots to overlap to some degree, which makes the technique usable for projectors and such.

I'm not sure how it will work out with these multimode lasers though: if you put the slow axes side by side, the pattern will remain something that looks like || over a fairly long distance. If you put the fast axes side by side, they will overlap sooner but you get an even more oval/rectangular output pattern.

Sometimes an image is better than words (for me, at least )


I just drawed the beams in different colors for better understand, ofcourse they are both the same color