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780 nm Laser Diode Array Build

theDUDE77

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I am very new to lasers so I wanted to get a little insight into my first build before I get started. Before I became a member, I spent a week going through this forum, other websites, and the parts I was intending on using. As the title suggests, I am very specific about the array that I want to build and I will give a brief summary for my intent. I am a chemist and there was a paper showing that a Lightscribe DVD/CD burner could convert soluble graphite oxide into single layer graphene with conductive properties. The papers and videos looked very easy and I was wanting to experiment with this in my free time. So I was going to buy one of the discontinued drives and some lightscribe DVD/CD's, but then I went down a rabbit hole and here I am. I want to make sure that I have all the parts and that they will theoretically work for a laser diode array.

The information that I have gathered is that the lightscribe burners use two different laser diodes but the one I am interested in is the CD laser diode and this puts out IR 780 nm wavelength. This is what activates the dye on the lightscribe DVD/CD's. However, I have not been able to find any other specs on the lightscribe lasers. I found that the actual burner specs are 5V <1000 mA typical, 1600 mA max but this does not help in deciding which laser diodes to buy. So I found a site about a Sony Drive that does 48X record speed using a 780 nm laser with 250 mW output so I will be going off of those specifications.

Now, everything I found about building a laser array was to combine the laser power into one beam which is not what I am trying to do. The only thing close was Styropyro's laser shotgun that uses a manufactured blue laser diode array which is the wrong wavelength, but does give some helpful information. What I am trying to do is to build a 2x2, 2x3, or 3x3 (4 diodes, 6 diodes, or 9 diodes) array depending on the limitations of the build similar to combining multiple led diodes to get larger light coverage but with the same intensity. Then, instead of using the burner, I could use this laser array and move across the surface material covering more area. Also, I would not be limited by size or having to use discontinued Lightscribe supplies.

So here are the parts I was considering. I realize they are cheapish and I am fine with that since this is my prototype.
  1. The diode specs are 780 nm continuous 200 mW and pulse 425 mW with a can type TO 18 at 5.6 mm found here: https://www.ebay.com/itm/10PCS-Sharp-GH0782RA2C-Infrared-IR-5-6mm-780nm-200mw-Laser-Diode/312421415487?hash=item48bdc47a3f:g:AksAAOSw2hxcIhuq
  2. The diode drivers were going to be 532nm/650nm/780nm/808nm/980nm Laser Diode Circuit Driver Board 0-800mha (it has a potentiometer so I'm assuming they meant mA). Because they are cheap, I was just going to use a driver per laser diode. Since it goes to 800 mA, it looks like I might be able to use 1 driver for 2 laser diodes but I wanted to make sure. Here is the link for those: https://www.ebay.com/itm/4pcs-532nm-650nm-780nm-808nm-980nm-Laser-Diode-Circuit-Driver-Board-0-800mha/222908654759?hash=item33e66424a7:g:WZoAAOSwJstawvmj
  3. And I was going to put the laser diodes into these 8x13mm Mini Case/Housing for 5.6mm Laser Diode Module w/ Dot Focus Lens found here: https://www.ebay.com/itm/5pcs-8x13mm-Mini-Case-Housing-for-5-6mm-Laser-Diode-Module-w-Dot-Focus-Lens/321596546278?hash=item4ae0a5dce6:g:eg4AAOSwkbdbSBDX
I want to line up the laser diodes in a grid and sink the cases using a drill press into a copper or aluminum heatsink. I might also use some of the heat transfer paste like Arctic Silver. Then I was going to put a fan on the heatsink with the fan pulling air through the heat sink and blowing up. I wanted the fan blowing up because I didn't want it blowing on the material below the lasers. Theoretically, I might be able to liquid cool using a PC system, but that gets more expensive and difficult. I might not need the fan but I figured with all of the diodes stacked together, it could not hurt. Also, I know heating can change the current so it might help keep everything consistent and stablized.

Finally, I was going to power this with a 30V 10A Adjustable DC Power Supply Precision Variable Dual Digital Lab Test found here: https://www.ebay.com/itm/30V-10A-Adjustable-DC-Power-Supply-Precision-Variable-Dual-Digital-Lab-Test/152857636147?epid=4012682122&hash=item2397066d33:g:bcIAAOSwIBJaUtij . This power supply will also let me mess around with other projects in the future. I understand that there will be more with wiring, capacitors, resistors, breadboards/circuit board, etc especially if I want to run everything off of the same power supply. But I like that the drivers and power supply are adjustable so I don't have to use more circuitry than needed. I am wondering if this is a sound starting point and will the power supply be sufficient. I won't know the resistance across all of the drivers, diodes, wires, etc. and this makes calculating a little more difficult, but I wanted to make sure the parts I listed will suffice since they are coming from over seas and takes time. I can always have a power supply or multiple power supplies depending on how everything is wired delivered quickly. I can also get all the necessary circuitry same day or next day delivery. Good laser goggles are also on my list for the project that are suited for a large range around the 780 nm wavelength.

Any feedback is greatly appreciated and I just want to make sure I am on the right track. I not looking for hand holding on this project because that is no fun for anyone. I plan on studying up on electrical circuits and diagraming my project so I can get a better idea of the calculations so I will know how to put everything together when the parts get here. I'll also take ample pictures and post as things come together. I apologize if I broke any of the newbie rules. I will do updates and edits as needed. I promise I perused the forum newbie threads and I searched multiple times for a build like this but came up empty.
 



paul1598419

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I would look into getting a fiber optic coupled array in 780nm. These can be found on eBay as well as other places. If you got this, it would save you a lot of hassle with trying to get it driven and either knife edged or coupled together optically into another fiber array. These are usually used to pump a solid state crystal, so most of it will be done already for you. Good luck.
 

theDUDE77

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May 6, 2019
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I will definitely start researching them. Eventually, I would like to cover about the size of a sheet of paper at one time. I may still buy the items I listed because they were only $50 bucks for 10 drivers, diodes, and holders, which is a cheap start and it gives me a good way to experiment with lasers. Plus, if the 780 nm diodes don't work, I can just swap them out with other diodes and wavelengths to play around with. Thanks.
 

Alaskan

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Must it be 780 nm? Can ~800-812 nm work? 12-40 watt FAP800 fiber output modules made by Coherent can be found on ebay at good prices from time to time. I've bought a few and used one with a big heat sink and 2.0 VDC 25 AH Hawker Cyclon lead acid battery without a constant current driver for a 40 watt output unit. The battery can run down in 10-15 minutes though, but that prevents the current from creeping up, as long as you have a big enough heat sink. If it isn't big enough, you might have an uncontrolled runaway and destruction of your FAP.

Running laser diodes without a constant current regulator is a bad idea, but with that particular FAP, that battery and my heat sink, it would never happen. It could, if I had twice as much battery capacity, or perhaps half as big a heat sink, then it might heat too much over time, but 15 minutes of run on mine wouldn't, as the power started backing off more and more due to lower and lower battery voltage, and that particular battery will only charge to a peak of about 2.1 to 2.2 VDC, perfect for a FAP.

I don't see many of these FAP800 modules on ebay for decent prices right now, but they show up from time to time. I've paid as little as $100 for one, occasionally you can find them for 150-200 each used, but they might have one or two of the diodes in the fused fiber output dark due to a dead diode, but there are like 19 of them combined into one output, so for our needs, not a big deal to me.

FAP800 Data Sheet:

Here's a FAP600 at a decent price, I have no idea if it is any good though: https://www.ebay.com/itm/COHERENT-FAP600-25W-805-0-Laser-Diode-1041806/283350134511?hash=item41f8fbeeef:g:S~UAAOSwwfFcSIlF

FAP600 Data Sheet:

Throwing in a few comments about this stuff in case someone new to this is curious:

Search Youtube for FAP800, there are several videos put up showing people burning things with them. You can collimate them with a PCX lens, I did with a 12.7 mm diameter one mounted in a holder with a SMA fitting on it which produced a divergence at infinity focus of about 16 mRad, you could use the same lens to focus to a point to burn. If using IR lasers in a pointer, for the size of the collimation lens, unless a single mode diode, they typically will have very poor divergence compared to our visible spectrum laser diodes, far higher than multimode vis laser diodes in most cases, except perhaps the blue NUBM44, that multimode vis laser diode has terrible divergence when used with small ~6 mm diameter collimation lenses, but some of the red laser diodes (not far from IR in wavelength) can also have very poor divergence. All of that said, single mode laser diodes will usually have fairly low divergence at any wavelength whether Near IR through UV. Diodes used to read and or write CD's are all single mode.

You can also find 30 watt 905 nm fiber output diode modules cheap from time to time, get with RedCowboy about his, if you have questions he will probably be happy to help.
 
Last edited:

theDUDE77

New member
Joined
May 6, 2019
Messages
9
Points
3
Must it be 780 nm? Can ~800-812 nm work? 12-40 watt FAP800 fiber output modules made by Coherent can be found on ebay at good prices from time to time. I've bought a few and used one with a big heat sink and 2.0 VDC 25 AH Hawker Cyclon lead acid battery without a constant current driver for a 40 watt output unit. The battery can run down in 10-15 minutes though, but that prevents the current from creeping up, as long as you have a big enough heat sink. If it isn't big enough, you might have an uncontrolled runaway and destruction of your FAP.

Running laser diodes without a constant current regulator is a bad idea, but with that particular FAP, that battery and my heat sink, it would never happen. It could, if I had twice as much battery capacity, or perhaps half as big a heat sink, then it might heat too much over time, but 15 minutes of run on mine wouldn't, as the power started backing off more and more due to lower and lower battery voltage, and that particular battery will only charge to a peak of about 2.1 to 2.2 VDC, perfect for a FAP.

I don't see many of these FAP800 modules on ebay for decent prices right now, but they show up from time to time. I've paid as little as $100 for one, occasionally you can find them for 150-200 each used, but they might have one or two of the diodes in the fused fiber output dark due to a dead diode, but there are like 19 of them combined into one output, so for our needs, not a big deal to me.

FAP800 Data Sheet:

Here's a FAP600 at a decent price, I have no idea if it is any good though: https://www.ebay.com/itm/COHERENT-FAP600-25W-805-0-Laser-Diode-1041806/283350134511?hash=item41f8fbeeef:g:S~UAAOSwwfFcSIlF

FAP600 Data Sheet:

Throwing in a few comments about this stuff in case someone new to this is curious:

Search Youtube for FAP800, there are several videos put up showing people burning things with them. You can collimate them with a PCX lens, I did with a 12.7 mm diameter one mounted in a holder with a SMA fitting on it which produced a divergence at infinity focus of about 16 mRad, you could use the same lens to focus to a point to burn. If using IR lasers in a pointer, for the size of the collimation lens, unless a single mode diode, they typically will have very poor divergence compared to our visible spectrum laser diodes, far higher than multimode vis laser diodes in most cases, except perhaps the blue NUBM44, that multimode vis laser diode has terrible divergence when used with small ~6 mm diameter collimation lenses, but some of the red laser diodes (not far from IR in wavelength) can also have very poor divergence. All of that said, single mode laser diodes will usually have fairly low divergence at any wavelength whether Near IR through UV. Diodes used to read and or write CD's are all single mode.

You can also find 30 watt 905 nm fiber output diode modules cheap from time to time, get with RedCowboy about his, if you have questions he will probably be happy to help.
Those wavelengths might work since they are close to the 780 nm and the higher wavelength pushes it more into the IR range. I only know that that Lightscribe was at 780 nm and 250 mW. So I would have to move the fiber laser module you recommend away from the material since it is much more powerful until 250 mW of energy was hitting the surface. I would probably need a laser power meter for this instead of just guessing the correct distance. Hopefully, I can experiment to see what other conditions (wavelength and laser power) would convert the graphite oxide to graphene. Ideally, I am trying to optimize a system that covers a large area and converts in a short period time without burning the substrate underneath. Thanks for the info and the data sheet. It gave me a good idea of power and size. Unlike most people, I am trying to cover a large area with consistent laser energy instead of focusing all of that energy into a very small area.
 

paul1598419

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Actually, you could expand the beam to cover more area and have 250 mW per mm^2. I doubt that you need to limit the power that much, though. It will take less time at a higher power to effect the same outcome.,
 

kecked

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Can you describe in a single sentence your objective. I skimmed your novel and have no idea why you want to do what you are doing. How does the graphene tie in and what is the final product meant to do? 780nm is used mainly for Raman because there is little fluorescence. It is used to see 2d vs 3D graphed structures vs graphite. Works well. Spell check hated this post
 

theDUDE77

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I would say it was more like a short story... maybe a novella. :) Graphene is what I want to make from graphite oxide. The laser energy is some how used to drive the reaction just like adding heat. Thats what I am trying to figure out. I want a large enough laser array to cover more area so that it coverts more of the graphite oxide at one time instead of having to wave one laser diode over the same area. Raman covers most of the IR spectrum (4000 cm-1 to around 515 cm-1 instrument units) and combines it into one spectrum.
Here is one article that describes the process if anyone cares to read. There are also videos that show the process.
https://scitechdaily.com/making-graphene-based-supercapacitors-with-dvd-discs/
 

kecked

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Interesting. I willlook into this more carefully.
 

Alaskan

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Need to get an idea of how much power density you need to accomplish the task, once that is known we can try to crunch some numbers to see how big you might be able to go, within a budget, as the wider the beam is, you will need more and more power to maintain the same power density.
 




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