How to polarize a beam

• Feb 18, 2011

• #1

LaserAdct

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Hello all.

I have found a lot of posts describing how to combine two beams into one using a PBS cude. What I can't figure out, and also can't find any info on is how to polarize one of the beams so combining is even possible. I have a couple of PBS cubes from PHR sleds and two LPC-815 diodes in Aixiz housings. Can someone try to explain how one of the beams can be polarized?

Best regards

Nicki

 

• Feb 18, 2011

• #2

andy_con

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Polarized Cubed Beamsplitter

 

• Feb 18, 2011

• #3

LaserAdct

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Thanks for that post.

If I understand this correct - polarizing a laser in this content simply means to rotate it 45 degrees on its own axis.

 

• Feb 18, 2011

• #4

Bluefan

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Polarizing can be done by adding a polarizer, but this is only needed for unpolarized light, laser diodes already give polarized light. You need to match the two lasers to the two polarisations the cube will combine, which in this case can be done by rotating one laser 90 degrees.

 

• Feb 18, 2011

• #5

LaserAdct

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Ofc 90 degrees don't know why I wrote 45. Weekend is incomming so my brain must be going in hybernation mode Thx

 

• Feb 18, 2011

• #6

Cyparagon

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Take note: the light polarization needs to be 90° different. That doesn't necessarily mean the lasers themselves will be 90° rotated with respect to each other.

 

• Feb 22, 2011

• #7

Krutz

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adding to Bluefan:
all lasers produce polarized light!
Laserdiodes even produce linearly polarized light by themselves, exactly what you need.

However, you can only combine two differently polarized beams. The resulting beam is then a mixture, which cant be made "linearly polarized" again. Thats why combining more than a few beams is such a pain.. ;-)

Manuel

 

• Feb 22, 2011

• #8

Bluefan

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Not all lasers are polarised, adjacent longitudinal modes in HeNe lasers are orthogonally polarized, YAG lasers are often not polarized, superradiant lasers are probably never polarized.
A property of stimulated emission is that the second emitted photon has the same polarisation, that's why so many/most lasers give polarized light (but this does require that the other polarisation has lower gain or something like it).