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ArcticMyst Security by Avery

Noob in over his head with 12 Watt diode collimation

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Ok here's the deal, I saw this deal on eBay for three 12Watt 942nm diodes for 20 bucks and I felt my manhood was on the line if I didn't buy em so they're presumably in the USPS on their way here as we speak.

Link to the ebay auction (he has more): NICE - 3 NEW? 942nm Laser Diode Modules - WOW! - eBay (item 140458093048 end time Oct-04-10 14:07:34 PDT)

ybdiode1-1.jpg


First of all, I've never seen diodes that look anything like the images he's provided. If anyone else has, I would love any input you can provide. Questions I'd like answered about it might include: wtf is that metal can on there? Why is there a thumb screw on top of it? Why is there what appears to be a hard drive jumper on the back of the package? Where will the light be emitted from... etc.

I'm hoping there will be some included paperwork with the shipment but I rather doubt there will be. I can't find any info about a manufacturer or anything from searching for part numbers and none of the image searches I've ran for diodes has turned up anything similar.

Second of all, from the pictures he's taken of some specification sheets, the "FWHM" is only 3.3nm. "Full Width at Half Maximum equivalent"... Is this referring to the deviance in the emission spectrum of the diode or something else?

ybdiode1-5.jpg


My third and final question is regarding collimation and/or focusing the output. I've got a pretty good 10mm planar-convex lens mounted in an aluminum assembly that's got really good transmission in my wavelength. However, when I purchased this lens it was very clearly stated that it was for Fast Axis Corrected diodes only.

I understand what Fast Axis means, what I don't understand is what the corrected bit means. Does that mean that the beam is collimated along one axis so it only puts light out in a line? Or does it simply mean that the fast axis divergence has been reduced to the same divergence of the slow axis so it spits out a square pattern?

Regardless of the answer to the previous question, does any one have any recommendations as to correcting the fast axis of one of these diodes for use with this lens? I'm probably going to shop around for more optics anyways but I'd love some advice.

Ok, now for my objective with this. I'm hoping to build an X-Y table and use one of these diodes to etch printed circuit boards, or etch a resist off of the surface of copper clad boards and then chemically etch them normally. Construction details of that end of the project I assume are for another forum, I just wanted to let you know what I intended to do with the end product of this crazy project.

Oh, and a P.S. Yes I have purchased applicable safety eye ware. I am not completely without sanity. Link: LSI 100-25-125 Laser Safety Eyewear

The filter is designed for YAG pumped lasers and has a healthy optical density around that wavelength so I'm pretty sure I'll be protected as long as I don't give it a chance to burn through. I'll take any input you have about the goggles as well.
 





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The jumper on the back is most likely shorting out the diode to protect the die from ESD damage from shipping or simply handling the diode.
 
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The light will be emitted from the tiny bar between the two \| and |/ shapes, it's a tiny brownish rectangle on the white part:

ybdiode1-2.jpg
 
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That's kind of what I was thinking, I guess that means the thumb screw is there to hold the electrodes down against the heat sink then.

If that's the case then do you suppose the wafer will be loose to where I could remove it and package it myself? Like say against an old CPU heat sink?

Do you suppose soldering directly to the wafer would destroy the diode?
 
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I wonder if the big thumb screw has something to do with mounting the diode, it does appear
to have a fairly large base. Collimating this beast from a diy stand point could be tricky.
 
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I love a challenge...

What really scares me is the different numbers on each of the \| |/ things. Notice the far right module has a 02 where the other two have 01's in the picture Prototype linked in.
 

Toke

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It looks to me like the screw on top is for the + wire and that - goes to case/whatever heatsink it is mounted on.
Collimating is likely going to be a pain.:(
 
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That's kind of what I was thinking, I guess that means the thumb screw is there to hold the electrodes down against the heat sink then.

If that's the case then do you suppose the wafer will be loose to where I could remove it and package it myself? Like say against an old CPU heat sink?

Do you suppose soldering directly to the wafer would destroy the diode?

Are you asking about the lasing die itself or the bits next to it as well? You can solder lasing dies if you're very good at reflow work and have steady hands, and a very good microscope.
 
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I was asking about the die itself. Yeah, that's a no then, at least for now. I don't even have a temp controlled iron yet.

I'm just looking for options for mounting the darn things, they look really awkward and I don't have any pics of the underside. Really hoping there's some threaded holes on the other side of that block of metal, if not I have no idea how I'm going to mount this to a heat sink.
 

Toke

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There are likely threaded holes on the underside for a long small bolt all through the heatsink. At least that is one way to mount hydraulic valves.
 
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Collimating something like this will not be easy, you'll want to get two cylinder lenses with differing focal distances. You will need to separately collimate the fast and slow axes to a fine point for the best energy density and cutting power.

High powered diodes like these emit light in a large rectangle hence the need for a lens on each axis. The one that spreads out more over distance is called the fast axis and vice versa the slow axis on the other.

Supplying power is also not so easy, you will need a driver capable of supplying about 2v at 12A. You could probably rig a 3.3v or 5v switchmode supply with a large resistor to create a very basic power supply.

This diode will also need good heatsinking, a CPU cooler or something similar should suffice. Bolt the diode onto the sink with some good thermal compound to ensure the diode stays cool.

Hopefully some of those bits of info will prove useful.
 
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Guess I'll figure up money and order some coated cylinder lenses from thor labs. Anyone know a cheaper place to get cylindrical lenses for near IR?

I'm not too worried about powering them, my friend designs power supplies for a living. I'll just trade him one of the diodes for a custom board. Before I do that I have a computer PSU converted to a bench-top supply that should work fine for testing purposes.

Same goes for cooling, I'm a computer overclocking enthusiast in my spare time.

Also, thanks to everyone for your responses and advice, I really appreciate it.
 
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Thanks a bunch dude, just ordered four lenses, cost me 43 bucks. Less than what it would have cost to buy one new one.

Got two lenses with a 9mm focal length and 2 lenses with a 24.4mm focal length. Hopefully they wont melt when I pump 942nm light through them.
 
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If you ordered glass lenses it will go just fine. I actually have a few lenses coming my way too from surplus shed, they had a nice sale.
I take it you already have a pair of suitable laser safety glasses?
 




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