combining beams

[badger1666]

i want ot combine two red lasers i know i need a polarised beam splitter
and that i should set one laser slightly off axis to the first to avoid one beam reflecting back and killing diode also theres somthing else that i dont know about what is set one laser at a different polarity all about it supose to aid combining the beam?
does anyone know about this

[MechEng3]

You will need one laser horizontal pol. and one laser set up for vertical pol. Then you will be able to combine the beams through the PBS cube . Do a "search" here. You will find lots of info.

[stanwax]

Badger
Basically you can only combine the beams when you offer them to the cube at different polarities. At polarisation A you set one laser so it shines through the cube - you will find that some red will be reflected by the splitter and you need to adjust the angle of the cube a few degrees so this is minimised. i.e. maximum light straight through. If you then shone the second laser at the side of the cube but with the same polarisation that too would go straight through but as its set at 90 degrees to the first laser then this would be pointless. If you position the laser diode within its housing so its at 90 degrees to the first laser (the straight through one) - or lets say polarity A+90 degrees - then when you hit the cube it will bounce off the 45 degree surface within the cube. All you need to do is get the two beams to converge at some far away point - the further the better but you need to be practical!
see attached image to see how you can tell the orientaion of the diodes - these are without lenses on.

Rob

PS I hope my waffling makes sense!

[badger1666]

thanks guys its all a big learning curve for us noobs and it guys like you that help and make life easier

[stanwax]

I know it may not be a great help but have a scan though the galleries to see if there are pix od how people have set theirs up. My dual red can be seen here ....http://photonlexicon.com/gallery/album72

but better - do as Mech suggested and search the posts there is bound to be a bounty of info waiting for you there

Rob

[The_Doctor]

i want ot combine two red lasers i know i need a polarised beam splitter
and that i should set one laser slightly off axis to the first to avoid one beam reflecting back and killing diode also theres somthing else that i dont know about what is set one laser at a different polarity all about it supose to aid combining the beam?
does anyone know about this

The other people posting have that question answered, but I can add something to the bit about avoiding reflections. First, set the laser that goes straight through on axis, then set the side one (with its quarter turn orientation to get the polar plane right) so it's not pointing exactly perpendicular to the first. That way you adjust the cube to get reflection of the second laser to go down the same axis as the first as it leaves the cube. The cube orientation will also make sure the first laser can't reflect back at itself. The angular offset will depend on how close your sources are to each other, and many other things, so you'll either have to experiment a lot, or do some careful modelling in software. If you're using expensive diodes, run them at the lowest power you can see easily (use faint fog), or use that software. Ideally both.

[allthatwhichis]

What kind of software are you talking of using?

Also, say you have two horizontally polarized diodes. Can't you just rotate one 90 degrees to make it vertically polarzed for combining?

[The_Doctor]

What kind of software are you talking of using?

Any kind of 3D modelling software will do if you make some basic forms. SketchUp will do it, and Google supply that for free. I've made models of acrylic asphere lenses and 5.6mm diode cans and a small PBS cube, if anyone wants to use them. This isn't virtual modelling, it's just a way to help you visualise layouts, but it's very accurate.

Also, say you have two horizontally polarized diodes. Can't you just rotate one 90 degrees to make it vertically polarzed for combining?

Yes. Though whether that's easy or not depends entirely on the mountings and layout.

[450nm]

A picture speaks a thousand words indeed! I've wondered about what the 'polarity' means and seeing the 'oval blobs' in your picture has made it perfectly clear.

I have a small (very) cube thingy from a DVD burners optics. Is this a combiner? If so would it be suitable to combine 2 reds?

Many thanks.

[badger1666]

hey stanwax looked at your dual dvd setup how well did using that dvd pbs work out if they are ok it would be worth buying a dvd burner just for the optics has anyone else had any luck with using dvd optics