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Do it Yourself Complete Green DPSS with O-like Crystals

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i see.
I thought it would be a great feature to have an IR laser change its colors, especially when experimenting with it and one needs to see the beam to see where it goes excactly
 

BShanahan14rulz

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A better way to think of it is not that the IR diode is changing colors, but that it is only used as a means to put energy into the laser cavity. The actual laser is the Nd doped glass crystal, not the diode, and it gains strongly at 1064nm wavelength. It just so happens that the particular crystal that is resonant at 1064nm also absorbs 808nm pretty efficiently, so it is an effective means of injecting energy into the laser cavity. It is this 1064nm infrared that "changes colors" through the use of a type of non-linear optic made of KTP.
 
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Wow...
And I thought DPSS was just slapping crystals in front of an IR diode lol

So all DPSS greens are hand-aligned? I don't see a machine making these teeny adjustments...
 

DrSid

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I believe the crystals are glued together, and mirrors are created on their surfaces, so there is nothing to align. Also the crystals are then sorted by efficiency, and the bad ones are thrown out. That's why it's so easy to get cheap underspecs green.
 
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I believe the crystals are glued together, and mirrors are created on their surfaces, so there is nothing to align. Also the crystals are then sorted by efficiency, and the bad ones are thrown out. That's why it's so easy to get cheap underspecs green.
That is the case in most green laser pointers/portables and most low-powered green lasers, up to 200mW or so, but at power levels above that discreet crystals such as the ones in the OP are usually used. They are coated on some facets, but the OC mirror is typically a separate unit. Any system that uses discrete crystals requires a good amount of alignment. Even the glued crystals require a small amount of alignment to get the best efficiency. The alignment is done by hand in pretty much all lower-cost non-scientific DPSS systems.
 
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My green laser pointer had the DPSS 1064nm built right into the brass mount behind the ktp crystal, and the ktp crystal bonded to the front of this. There is no output coupler mirror in front of the ktp crystal (its likely between the ktp frequency doubler crystal and the DPSS laser crystal, inside the assembly and I can't see it without cutting the assembly open with a hacksaw). This is a lot more compact than your tutorial. If I wanted a DPSS laser, I'd just take this DPSS+KTP module and put it in front of any 808nm laser diode to power it, very easy, not complicated like your tutorial.
 

Exerd

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I managed to find a store on ebay from Australia that deals with crystal sets. I was hesitant at first to buy the higher end set. But then after chatting with the tech for some days I decided I would go for a cheaper package he had available. He told me he had obtained 600-700mW using a 3W pump C-mount in one of the sets like I received. The photos and items looked like they were selling quality "unique" laser items, I guess you could say.

So I bought the lens/crystal/heatsink assembly from this company. This consisted of a brass cylinder of, I believe around 20mm diameter (I can go grab it from the shop for details), a threaded rear brass cap, pre-glued crystal set, 2 diode-to-crystal collimating lenses, 1 IR filter, 1 final collimating lens pre-glued.

The only trick, I guess, is that the user aligns the diode.

My Big Mistake

This unit came with a 5.6mm diode flush/press mount. I was not pleased with that for a pump size. How could I be? The unit heat sinking was so extensional for a typical mount it begged for more than a 5.6... So I drilled out the diode hole with a mill. Accept, I screwed up the mount. Minor? Ehhh, majorly, you could say. I improperly used a drill bit size which was a number value off in the set, and I probably have 0.05mm of play all the way around the diode. No press-fit here. (Remember how they say, "you can always drill a hole bigger, but you can't drill it smaller"? Take my advice, always step in drill sizes carefully when you are trying to get the size right. ;) ) So I may have to use a ring for a 9mm diode to larger hole adapter, and then bore the heat sink out again to accept the adapter ring + diode, to fix the problem--if I want to properly.

I used a 1W 9mm 808nm pump diode. I was watching TEM00 change to other values as I wiggled the unit and diode around, which was very neat to me as I experienced the modes of the electron states changing on the wall. Then, I would hold the unit (and diode wires) while doing this goofy experiment, to try to literally hold the diode into the brightest TEM00 I could see on the wall without the collimating lens on. At very first there was nothing. No lasing was occurring. Ten seconds in I moved the unit and saw the first burst of light. Long story short, I thermal epoxied the diode in TEM00 while eyeballing it and let it set overnight. I obtained 98mW of green 532nm light on a Laserbee meter. I was impressed this very very sloppy setup actually produced near 100mW of green.

This thread reminded me of the module. I want to go dig it out now and look at it hah. :D
 




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