Combining two NUBM08 with Dichro (no PBS involved)

[Light superglue]

Sorry I did not have time to post in LPF more often.

But here is one interesting thing I have found when testing 445-462nm Dichro mirror from Live Lasersystems with some of new LDs purchased from DTR for this purpose.

From two NUBM08 he sent me (one with G-2 and another with stock lens) one produces a beam passing through the mirror at 96% (6.50W vs 6.74W with no Dichro mirror on the beam path). And the other unexpectedly produces a beam with 97% reflexion (5.90W vs 6.08W).

I think that this confirms the point discussed earlier in NUBM44 thread that less efficient LDs produce higher WL and also could mean that the range of WL from 05, 06 and 08 can vary a lot in (and maybe out of) range of 450-460nm we read in specs. I see similar behaviour with 05 and 06 but still need a time to collect more data.

If anyone has several 05, 06, 08 and such a dichro, maybe you could try this, too and in this way we might get more statistics about which LD type has more chances to be combined with NUBM44/47 (which beams are always in Pass range). Still it looks to me that finding such an LD other than 07 is a chance of the draw...
It anyone has a whole block, it would be interesting to find out if all 8 LDs in it emit in similar WL or not.

Here the pictures of combining setup. Both LDs are connected in series with 4.5A current and the new LPM is always not calibrated, so it reads 16.1W when should be 12.4W max. Sorry for that.

 

[10fenny]

Where did you get that optics board and mounts?

 

[diachi]

Good real world example in the wavelength variation between diodes! Cool discovery. This is why experimentation is good!

10fenny - not sure where OP got theirs, but those little ones pop up on eBay from time to time.

 

[Light superglue]

The breadboard here is the smallest metric one from Thorlabs:

https://www.thorlabs.com/thorproduct.cfm?partnumber=MB1015/M

But be aware that with VAT and delivery the price I paid for it added to almost 100EUR. Anyway it is perfect as the base for laser combining experiments.


Mounts and heatsinks: In the past I have tried many from ali, ebay etc. but 99% were crap. Finally what you see on pictures are combinations from:

3-axis adjustable mounts

13.5mm Adjustable Laser Pointer Module Holder Mount Clamp Three Axis Sale - Banggood.com

2-axis adjustable mounts (here you have to ask for biggest 23.5mm HS holder size)

https://www.aliexpress.com/item/13-...32275913077.html?spm=2114.13010608.0.0.MYbYJU

22mm Al Heatsinks from DTR

Also: it is very important to keep incidence angle 45° when combining.
At slightly different angle let us say 30 or 60° the beam which should pass the dichro can be mostly reflected.

 

[badboybilly]

So I see now who's VDL LPM abarrnett customer was, so you got it uncalibrated from Mitch!

 

[Light superglue]

Yes, this is what I got. Do you have these pics from AB?

I thought that AB would check LPM made by Mitch before sending to me but he apparently did not. I would not even notice that the readings are not correct if I had not the 2nd old LPM to compare.

But maybe all DIY LPM builders are not very careful with calibration. If there are not many customers having 2nd LPM who would notice the error?

 

[badboybilly]

Yes it was about the same time I got my LPM from Mitch and Alex sent me the pics, my LPM was calibrated very accurate, I'm not sure why yours wasn't there were a few things Alex wasn't happy about with that LPM I think one was there was no peak power reading if I remember correctly.

 

[Light superglue]

What is the power range of one you have?

 

[badboybilly]

I think it was 50w possibly more if I cooled the Ophir head, but mine is nothing compared to yours it's not liquid cooled. I doubt I'll ever need a 150w LPM but who knows.

 

[Light superglue]

This was probably silly of me to ask for the strongest LPM Mitch could do.

To my enquiry regarding the error he answered that when me asking for 150W capable LPM he thought that I am not going to use it for anything weaker than 100W. So he calibrated it in 100-150W area, and low power area (10, 20W etc.) "may have some mesurement error".

However, I was surprised that a LPM "up to 150W" will only be precise in its upper range and not all along the scale.

Anyway, finally I think that I need to find someone who has a LPM calibrated to 20 or better 50W and send him the thing to make a wattage comparison chart.

 

[paul1598419]

As far as the WL change, it would be great if you could find a spectrometer to confirm the shift. I had mine out yesterday and was doing some comparison testing. It takes all the guess work out of situations of this nature. I do like the mounts you got for your heat sinks. I need to start thinking about getting an optics bench and the three axis adjustable mounts for modules, mirrors and such.

 

[Light superglue]

Hi paul,

Yes, a spectrometer would be the ultimate tool to support my results but I do not have any. I am chemist, not math scientist, in this way I am used to prefer practical experiments over theory... So I suppose that someone better equipped can continue with my "accidental" findings and do more out of it...

But I have this Dichro and logically if one beam passes and other is reflected - they should have different wavelenghths. Unless next experiments result in something contradictory.

At the moment my mind is busy designing a device to dichro-combine 2 NUBM44 with PBS and 2 longwave NUBM08 with another PBS in order to have a 20-25W single blue beam as output. With all necessary waveplates and correction optics.
This may take months to assemble but I like to face the challenge.

 

[paul1598419]

Well, I wish you luck in your new project. I'll be looking forward to seeing it in a post when you finish. + Rep.