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PBS cube troubles. Pictures

Down with Umbrella

Down with Umbrella

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Hey everyone, I am just getting into optics and am having a few issues.. Ill try to explain this best I can and can provide more pictures.
I am trying to combine two 445 beams into one. I ordered a 445 coated PBS cube from stanwaxlaser.
The problem I am having is it seems no matter how I orientate the cube the beam passes straight through. It's also splits the beam in two directions.

If that's true when I have both lasers up and running there will be a reflection from laser A directly into laser B. is this normal? could that damage the diode? Is this a problem with the cube quality?
image_zps7622256f.jpg
[/URL][/IMG]

I've rotated the cube 90deg. several times and the beam tends to go straight through but splits the beams in different directions. I am provide more pictures.
image_zps3c5ef52c.jpg
[/URL][/IMG]

In the photo the beams are going ^>
image_zps3a3ac659.jpg
[/URL][/IMG]

Thanks for looking.
Jefferson
 





jander6442

jander6442

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Sorry I have not gotten back to you on our PM's I was at the Daytona race while you were corresponding.

I would suggest that you simply flip the PBS cube upside down and then try rotating the orientation of the "B" laser.

If that doesn't work then chances are that's a beam splitting cube NOT a PBS.
 
Down with Umbrella

Down with Umbrella

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Advice taken. This is the best result I was able to achieve.
From this angle the reflections are minimal but the "red" arrow still has a power output high enough to burn cardboard. To mock up the final build I tested the cube with another 445 build. without the cube the laser measures 2613mW.

Reflected 1879mW
Passed 767mW
(33mW lost in cube) I can live with that.

Note: in photo is both lasers powered up. In the test listed above only the laser being reflected is turned on.( Laser A)
According to my Calculations 28.9% is being passed through the cube and not being reflected ( red arrow) 767mW
image_zps8d2c66c4.jpg
[/URL][/IMG]

Hmm
 
crazyspaz

crazyspaz

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The PBS should output 2 oppositely polarized beams from one input, right?
 
Down with Umbrella

Down with Umbrella

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Right now this is just a mock up for the finial build. I was trying to decide how best to Orientate the cube. The cube is not polarized. I have a 1/2in 445 wave plate I haven't added in yet.
 
jander6442

jander6442

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I think you are simply over powering the cube. Try using some less powa 445's and see what happens. Please tell us where u got that PBS link or something to help use help you.
 
jander6442

jander6442

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Down with Umbrella said:
Advice taken. This is the best result I was able to achieve.
From this angle the reflections are minimal but the "red" arrow still has a power output high enough to burn cardboard. To mock up the final build I tested the cube with another 445 build. without the cube the laser measures 2613mW.

Reflected 1879mW
Passed 767mW
(33mW lost in cube) I can live with that.

Note: in photo is both lasers powered up. In the test listed above only the laser being reflected is turned on.( Laser A)
According to my Calculations 28.9% is being passed through the cube and not being reflected ( red arrow) 767mW
image_zps8d2c66c4.jpg
[/URL][/IMG]

Hmm
Click to expand...

Also in this pic the beam entering from the left see if you can rotate it while using an LPM, you should see the sweet spot when the LPM registers the lower number. After that you have done all you can, either lower the power or get a better coated cube if one is out there that can take that abuse:lasergun::D
 
ARG

ARG

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You should only be getting a milliwatt or so out the other side. Turn on one laser at a time and roatate it clockwise until no light comes out that side, then do the same with the other laser.

Your problem is most likely the polarization of the light entering the cube, I highly doubt the cube is the problem.

Edit: It may help to mention that in my testing of these cubes from stanwax I got over 99% efficiency with 450nm. With proper polarization you should get the same results.
 
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Down with Umbrella

Down with Umbrella

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ARG said:
You should only be getting a milliwatt or so out the other side. Turn on one laser at a time and roatate it clockwise until no light comes out that side, then do the same with the other laser.

Your problem is most likely the polarization of the light entering the cube, I highly doubt the cube is the problem.

Edit: It may help to mention that in my testing of these cubes from stanwax I got over 99% efficiency with 450nm. With proper polarization you should get the same results.
Click to expand...

Ah ha! Thank you both Jander and ARG for picking up on this. I rotated the laser counter clockwise until very little/none light was being passed.

My problem now is on my project both modules are set almost perfectly like this: _ _ rotating these modules to find the "sweet spot" is going to be pretty difficult at this point.
 
ARG

ARG

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Down with Umbrella said:
My problem now is on my project both modules are set almost perfectly like this: _ _ rotating these modules to find the "sweet spot" is going to be pretty difficult at this point.
Click to expand...

You can use a 1/2 waveplate (also avaliable from stanwax) to change the polarization of the light without rotating the modules. :)
 
Last edited:
Cyparagon

Cyparagon

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protip: polarization coincides with the beam profile when it comes to laser diodes. These blues have an obvious shape to them - a bar. The orientation of this bar will either need to be vertical or horizontal. "rotate until you find the optimal position" will always result in one or the other, and the second laser will be the complement. Therefore, the final beam will form a plus shape.
 
Down with Umbrella

Down with Umbrella

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I corrected the beam with the waveplate for laser "A" now it looks like I need another waveplate for laser "B".
 
ARG

ARG

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If they are currently the same polarization going into the cube you will only need one 1/2 waveplate to combine them. Two 1/2 waveplates would just make it the same polarization again.
 
Down with Umbrella

Down with Umbrella

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I think what I'm going to have to do is manually roll module "B" just a hair to clean up the reflection in the cube.
 
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