beam combiner question

[asd]

Hello,

I'm new to this forum and lasers in general.
But I've had a lot of fun reading about lasers online.
And I was wondering if anyone knew if beam combiners can
combine lasers when there going the opposite direction????

I guess you wouldn't want the lasers pointing directly into each other... ha
but you could have the source of the lasers be off centered to the beam combiner.

[c4r0]

You can use polarizing beamsplitter in case of combining two beams of the same wavelength (not cube beamsplitter, actually I'm not sure if there are any polarizing beamsplitters that are not cube shaped), or a dichroic filter in case when two beams has different wavelengths. Generally it will work with 0 deg light incidence, but the combined beam would be directed to one of the lasers, so it's useless.

[Insanity]

You do it like this:

Same wavelength with polarised beamsplitter cube:



And different wavelengths using dichroic mirrors:



Mark

[asd]

thank you!!!
At first I wasn't really understanding how you can combine a beam with a splitter?
ha but then I realized you just do it in reverse... right?

Mostlly everything I'm seeing is combining 2 beams 90 degrees away from each other with that
cube.... But I geuss I am wondering if you can have two beams 180 degrees away from each other
and combine them.

[c4r0]

Splitter is just a name and it can be used to split one beam into two beams or combine two beams into one. Combining and splitting beams is practically the same physical phenomenon, but kind of reversed. Splitter is simply an element that transmits light that has given properties and reflects light with other properties (like wavelength in case of dichros or polarization in case of polarizing splitters). As I wrote before, combination of two beams 180 deg is possible, but the output beam will hit one of the lasers, so there's no point doing such thing. People mostly combine beams directed at 90 deg to each other because it is the most rational way. When you're combining two beams with a dichro you can use other angle than 90 deg, but notice that dichro's transmition/reflection vs. wavelength chart depends beam's angle of incident That means that you can 'tune' a dichros bit by changing the angle of incidence

[Insanity]

If you use a PBS cube, you need to have one laser horizontally polarised and on vertically polarised. If not you have to turn one laser on its side like I did in the pics above...

If you have the lasers facing each other, you could steer one with a mirror to replicate the 90 degree angle, but every optic costs a bit of power....

Mark

[allthatwhichis]

You do it like this:

Same wavelength with polarised beamsplitter cube:



And different wavelengths using dichroic mirrors:



Mark

This is one of the purdier examples...

[c4r0]

If you use a PBS cube, you need to have one laser horizontally polarised and on vertically polarised. If not you have to turn one laser on its side like I did in the pics above...

Just to mention, if it's not possible to mount the laser on it's side you can also use a half-wave plate to rotate polarization of one beam by 90 degrees (with a bit loss of power)