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Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

Julian95

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

The light from a laser diode is already linearly polarized.
sorry i'm not very familiarized with this, which laser diodes are the ones that emit polarized light?, i know there are a couple of different types used in telecommunications that do, but in power lasers?, are they all polarized?
 
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Light superglue

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

Hi Diachi,

I am happy to see that you understand my question now.
Would there be any rules prohibiting to make such a PBS with rotated polarisation?
All PBS cubes I have (and I have many of them from different suppliers) work the same. But I am still searching...
 

diachi

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

Hi Diachi,

I am happy to see that you understand my question now.
Would there be any rules prohibiting to make such a PBS with rotated polarisation?
All PBS cubes I have (and I have many of them from different suppliers) work the same. But I am still searching...

Can't see any cubes that are rotated.

However, what about using a PBS plate and rotating the plate 90°?
 

jors

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

Can't see any cubes that are rotated.

However, what about using a PBS plate and rotating the plate 90°?
Do you know where to purchase those polarising plates? thanks
 

Light superglue

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

If you mean those PBS plates Thor sells at 335EUR + tax, then this is not price for me. Also, they do not have them for blue.
From Edmunds it looks that they are very fragile - so now I better understand why everyone is using cubes - 2nd shape from the ones hardest to break (after sphere of course):yh:
 

Light superglue

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

After a long period of time got some free days to tinker with my yet unfinished 4-beams combiner. But forgot that the B-B Dichro had only one reflecting side.

So when I finally attached all glass pieces and adjusted mirrors – it was a bad surprise to see that I accidentally placed Dichro in reverse – the light reflected from the back side and the resulting beam was ~2 mm shifted to the side from where it was expected to be!

So I had to detach all pieces and put them back again. Then combined both pairs of NUBM06 (bottom line) and NUBM07 (top line). All 4 lasers are with original G-balls. By the way Eagle pair googles stop much more light compared to ebay ones – check the pictures!

Then combined lines vertically and now trying to glue LSP cylindricals to the 3 empty mounts left. And already found 2 issues here:
- no matter how many times I tried to combine the thin vertical lines (beams close range), after 6x expansion it is clear that the centers of expanded beams are pretty separated

- positioning CYL mounts to have 35mm separation was not very right thing to do. CYL had to be 32mm separated to have round spot at the wall 5m away where I check it. Maybe it is because I try to focus and not to find “infinite focus” but 3mm seems a pretty big difference from what was in specs from LSP. Has anyone found this before?
 

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Encap

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

After a long period of time got some free days to tinker with my yet unfinished 4-beams combiner. But forgot that the B-B Dichro had only one reflecting side.

So when I finally attached all glass pieces and adjusted mirrors – it was a bad surprise to see that I accidentally placed Dichro in reverse – the light reflected from the back side and the resulting beam was ~2 mm shifted to the side from where it was expected to be!

So I had to detach all pieces and put them back again. Then combined both pairs of NUBM06 (bottom line) and NUBM07 (top line). All 4 lasers are with original G-balls. By the way Eagle pair googles stop much more light compared to ebay ones – check the pictures!

Then combined lines vertically and now trying to glue LSP cylindricals to the 3 empty mounts left. And already found 2 issues here:
- no matter how many times I tried to combine the thin vertical lines (beams close range), after 6x expansion it is clear that the centers of expanded beams are pretty separated

- positioning CYL mounts to have 35mm separation was not very right thing to do. CYL had to be 32mm separated to have round spot at the wall 5m away where I check it. Maybe it is because I try to focus and not to find “infinite focus” but 3mm seems a pretty big difference from what was in specs from LSP. Has anyone found this before?
Have you laser power metered the output yet?
 

paul1598419

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

I guess I was expecting the lines to overlap one another instead of having separate spots at the end.
 

Light superglue

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

LPM checks will come later. First I wanted to combine and correct all beams at 450-550mA current.

Yes they are overlapping but I meant that it is difficult to make them overlap perfectly. Here was the pic without cylindricals but after cylindricals are added this apparently perfect 1mm thin line becomes >6mm thick and by switching on/off the beams I see that they still are ~2mm off the common center.

What means that an additional adjustment of mirrors will be needed after I will have found the right positions for cylindricals...
Not easy the job to combine many beams!

Sure the right way to proceed would be expanding beams prior to combining but in this setup I wanted to keep the footprint of baseplate 70x120mm. That's why I try to use half-length DTR modules, very small mounts and avoid long G-2 lenses etc. Because I still hope to be able to mount it on a not very big RC tank chassis or into a Fenix TK75 host as if I am correct Alaskan or RC once suggested.
 
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Light superglue

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

Sorry, forgot to add pictures to previous post.
 

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Light superglue

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

Finally added Cylindricals to the setup.
To do this it was necessary to attach an additional mount for PCX to keep beam path between CYL surfaces 32mm instead of planned 35mm.

Also a holder for Sanwu BE adapter is on place now - the hole serves as spacial filter at the moment.
Pic.3 is only 06s on (450mA), pic.4 only 07s on (550mA), pic.5 all 4 LDs on.

Also the spot at 5m does not look essentially bigger than just after "spacial filter" both through good and cheap googles. Looks fine, no?
 

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RedCowboy

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

Quite the project you've been working on, keep it up and good luck. :beer:
 

paul1598419

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

That beam looks soooo much better now. Glad you got it worked out.
 

Light superglue

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Re: Need "Reverse" PBS for 20W "laser tank gun" prototype - do they exist?

Oh, holy shit.

It is really difficult to make such a setup for the 1st time.
After correcting the beams I have started to increase the current and what did I found?
At 2.3A the final outputs of each of 06 LDs measured alone were:
2.68W
2.38W

At 3.5A:
4.24W
2.56W only!!!

So, the 2nd 06 (beamed through WP) had a beam half-reflected from Blue-Blue-WP at high powers!

Long story short it had to be placed down under! What can mean that this BB dichro is sensitive to the direction of polarisation - it does matter if polarisation is rotated 90° or 270°.

In contrary, the other 06 (which beam does not pass through a WP) can be placed either up or down under - it does not matter, the beam is always passing the BB-dichro...
Now again I need to find a way to fix the unexpected issue...
 
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