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Not symmetrical box reflection on laser diode

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Hello,

As you know, when using G2 lens a reflection like a box are projected.
It's not dependant from model of diode.
Symmetrical or not symmetrical vary from diode to diode.

You can get this two case (Symmetrical or not symmetrical projected reflection) on singlemode or multimode and for any wavelenght.

But why we get this "problem" on a industrial machined process ? "diode dies can be badly aligned ?"

My picture show a multimode green perfectly manufactured (NDG7475) and a not symmetrical blue (NDB7875). I have a symetrical NDB7875 blue also !

- And you, do you get symmetrical/centered or "misaligned" reflection on you diode (and what model) ?
- Anyone for a more technical explanation on diode manufacturing tolerance and why we can get this ?

Thanks
Pascal

EDIT : it does not vary from one diode to another from same model.
 

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That is odd, maybe you should put up a picture of both the 7875 diodes at the same time :thinking:
 
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That is odd, maybe you should put up a picture of both the 7875 diodes at the same time :thinking:
Sorry the good one is mounted on a projector:)

Green NDG7475 have exactly the same divergence and box reflection as the blue NDB7875

You can use a swap color filter and you get it :crackup:
 

DTR

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If you mean on the blue that seems ringt. Here is a picture from the NDG7475 thread I posted two years ago. If every single one is like this I don't think it is misaligned or a tolerance issue it is just how they are made.

 
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DTR

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Here you can compare the NUBM44 with my NDB7875

Yes I get a perfect symetrical NDB7875 :D
I think he means how the spot is over to the left of center of the splash line that is at the top of the box reflection like in all three pictures. It would appear that is how they are made.





 
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This is like DTR say because I just mounted my spare singlemode green to check it, and I get exactly the same not-symetrical reflexion (exactly the same placement on the box)
 

DTR

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Actually it would probably be more accurate to say the box reflection is not centered on the spot than the spot not centered on the box as I am pretty sure the spot is dead center and the box is offset to the right.
 
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Yes all NDB7875 come like this, checked on a old ebay module with this diode.
I was misled by my 3.5W NDB7A75 with a LFL lens clone (symetrical and smaller box reflection)
 




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