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I burned a wave plate by putting too close to Ball lens

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I was playing with the “Tank gun” device which as some of you may remember was supposed to combine 2 NUBM06 and 2 NUBM08 (all LDs with Ball-lenses in place). But for the reason that the beam of 08 passes through Blue-Blue dichro at low currents (less than 3A) I replaced both 08s by 07s (having Ball lenses as well) to adjust optics at low power. Now all looked fine, even divergence was similar (lines of similar length at 5m, two up are from 07s) but measuring power I just noticed that the output of one of 07 became ridiculously low - 0.99W at 2.3A. Of course the LPM was after all of the optics (WP, PBS, mirror and Dichro), but 2nd 07 gave output of 1.76W and both 06s – 2.83 & 2.81W.

So, I checked what happened and noticed a small oval spot in the center of one of 2 wave plates which were installed in the very thin space between Ball-lenses and PBS. Interesting that the WP at the issue of 06 was not damaged. Half of the beam passing through this matt spot is scattered. Not sure if 08 could have done this before I replaced it by 07 but most probably not. Maybe it would not have happened with G-2, maybe the reason is that some of G-ball lenses focus the beam at 5-6mm but it looks that polarising optics does not support high light intensities.

And now I understand why many old members suggested to expand the beams prior to combining. To do this I will have to redesign the whole setup…

Maybe most of you knew this but anyway I want to warn those of you who would like to start combining high power LDs.
 

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Alaskan

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Darn, I've heard that too but didnt consider a wave plate could burn. does it have a coating or just the material itself burned? Can you move the wave plate a bit off to the side to use it?
 

RedCowboy

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In order to manage the beams I wanted to correct them all first, having to expand 1st adds more steps, was it a quality wave plate or a cheap one?
 
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Yes, the matt spot is only in center, rest of the area is intact but in order to shift the WP by side I have to debond it and it is not easy. Both WPs were glued to this brass piece with superglue and I already have kept it 1 week in water without success (common superglue is usually debonded by water in 24h). The glue we make at work is too strong!

All WPs I use are from Optlasers. I do not know is there are any more sellers with acceptable prices apart of this one.
 
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paul1598419

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Acetone will dissolve super glue in a heart beat. If you don't have any, fingernail polish remover will work in a pinch. Yeah, there are many different types of WPs. Some are made of mica, while other are another birefrigent material. Hope this helps.
 
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Re: Resolved - I burned a wave plate by putting too close to Ball lens

Hi Paul,

Yes I know about acetone but I was not sure if there was any coating on WP which could dissolve in acetone as well.

Finally after some more days in water the WP fell away and I could clean it with vodka.
Now the WP is fine - the 07 output through the optical trail makes 2.3W at 2.3A what seems reasonable to me.

Most probably it was a dirt burned on surface what made the beam scatter.
Anyway in the future I will not make setups so compact that there is no way to access glass parts for cleaning...
 
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A little of revival for an old thread to show how the issue was resolved.

In fact the WP was not burnt. I kept the pieces in water, then methanol to debond, then cleaned and rebuilt the setup. It took a lot of time but now the beams are adjusted pretty good again producing one line at close range (on flax oil bottle) and on the wall 5m away.

One thing to add: I broke my old googles from Novalasers (the company does not exist any more) and bought a cheap googles from eBay. These are really crap (at least for this WL) - you can compare pictures taken with phone!

Do you think that an Eagles pair from SL would match my old googles quality?

Oh yes, the output.

Now at 2.3A the 06s give 2.97 and 3.06W
The 07s give 1.99 and 2.37W
Total is 10.39W.
Hopefully the ouput will be 1.8x at 4,5A...

Next step is to add cylindricals (and BE) but this will be in another thread.
 

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paul1598419

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Glad to see you are still working on this. If there is a coating on a WP, it should at least survive alcohol and distilled water. Can't say what acetone might do without knowing what the coating is made of. Even if you removed the coating from the WP, it should still function with minimal reflections. Good luck, buddy.
 




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