Budding Enthusiast Needs Alignment Answer

Greetings from Southern AZ. I'm just getting into the laser hobby but I've always been excited about just about anything that lights up or has a turbocharger. I'm also into making stuff faster, stronger... and brighter.

Prior to doing any real research, I pot modded my green laser. Before you post all the "don't do it" links, I now know thanks to these forums. I also know not to disassemble the parts I already disassembled, and not to look into the dim red light I already looked into - OK kidding on that part. I will also be getting goggles as the now broken greenie did burn stuff.

So here is my question:
I have read that proper alignment is critical for our little green friends. I just can't seem to clarify exactly what that means in my head. As you can see from the pics below, there is a pretty clear line where I separated the expanding lens from the pump diode housing. If the pump diode is good, shouldn't there be some position of the expanding lens/KTP assembly to make it green again? The pump diode is definitely good. I can see it reflecting red light off my black couch which I also burned with the laser prior to it becoming an empty host.





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In order to feed my new found hobby, I bought 3 cheap 5mw pen style pointers. Green, Red, and Violet. My Jack Russel LOVES them, the cats barely care.

There are 1 to two crystals and two mirrors (more commonly these days they are sandwitched together to make one monolithic crystal and coating assembly) which have to be at the correct spot in all three axes ( X, Y, and Z axis) for the energy density from the pump to be phase matched and high enough to allow NdYAG lasing which makes the 1064nm invisible light. The KTP comes after and also needs to be phase matched and correctly aligned in all three axes for it to efficiently double the light to 532nm green. The lenses after the pump but before the crystal assembly are there to get the pump's light at the density needed. The lenses after the KTP are to fix the insanely bad divergence and collimate the beam.

The beam needs to enter the crystal set at just the right angle a focus. Ive done a little experimenting with these combo crystals with moderate success.



It took me a good five minutes just to get it stay laseing long enough to get my camera ready. It shows the beam remarkably well in the video, if i remember correctly it was actually no brighter than 10~15mW

Sure you can potmod a greenie as long you keep the current below the max specs for the specific IR pump diode. It´s just almost all new cheap greenies are already running at it´s maximum current and people are killing the pump diodes by potmoding them. That´s why others will warn you not to do that.

Like said the cristals are now sandwiched together all together with the coated mirrows. So they are a completely laser unit now that just has to be pumped with IR at a correct angle. The lenses are just making the beam a bit thiker and correcting the horrible divergence of such a "sandwich".

Here is how I alligned a cristal set sitting directly on the IR diode. You have to turn the cristal set clockwise or counterclockwise and find the sweet spot. This is very critical because you have to find the exact position where the IR hits the cristals at a specific angle for it´s max output.




And this is the result.

Thanks for all the info! So if I'm understanding correctly, it is theoretically possible, albeit very unlikely, that I could make my green laser function again.
I also read somewhere that I could have baked the crystals. Is this really possible with a laser that barely made black stuff smoke?

Could I just buy one of DTR's 445 M140's and run it at ~250mw with the existing plastic lens in the xx-850 host pictured below with the driver I have and a very short duty cycle? I'm planning on using an old 2C Maglite I have to house a real heatsink for a more powerful setup in the future.

It´s not just theoretically possible The above pictures were made while repairing a grenie with a died IR diode. I replaced the diode and realigned the cristals and got 170mW out of it. All you need is a still working IR laserdiode and enough of time to find the sweet spot of your cristal set. A LED´d IR diode will still emmit some IR light, but not coherent and not strong enough.

Also. You can´t use that driver for a M140 diode. Such a blue diode needs a different driver, an Axiz housing and AR coated lenses for 445nm. The module in your picture is also having glas lenses but they are coated for green light and do have a different focal length. So simply forget about this idea. Either build your blue laser with the correct parts, or buy one. DTR offers all you need to build one. Not just diodes but lenses, drivers and so on.

Btw. It´s really a waste for such a diode to be driven at just 250mA.


Forgot to mention. Yes, the cristals can get demaged if they get pumped with more IR they can handle and get overheated. So it´s not just important to keep the diode cool enough, but the cristals too.

Thank you! I appreciate everybody taking the time to answer my questions which have probably been asked before. I did search, but couldn't seem to come up with definitive answers, so thanks again.

I didn't realize there was state the pump diode could be in where it still worked, but at reduced power. That's probably the actual issue with my laser.

Thanks again everybody.

I think I'll take a crack at fixing this thing. I was able to get the diode out OK, so I'll just get a cheap 808nm and see if I can revive it.

HI Ishootstuff
Good luck with your repair and use the proper safety goggles for the IR diode.

Also a +1 for doing research before posting. And welcome to LPF:gj: