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Thread: Corning G-1000 module

  1. #1
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    Default Corning G-1000 module

    So, I've got the little G-1000 module here out of a pico projector. I've been doing some looking around, and found the laser driver IC they use for the pico projector: the MAX3600.

    On that page, it specifies: "For operation with synthetic green lasers, the driver includes a periodic off function and a fourth output with a random-noise generator."

    Now, these little modules have 4 input connections. 2 are for the diode, I am assuming, however there are 2 more that go to a little TEC looking element. I'm not sure if it's actually a TEC or a heater, but the "fourth output" thing described above leads me to think it might be something else. Here is an internal pic, thanks to "impulse" from LPF:



    The bottom device is what I assume is the pump diode. Is there a safe current I could start out driving it with, and seeing if I can get anything at all from this module?

    The 2nd question, what could the little device at the top be, and it's requirements? I've noticed a slight green output before, just driving the laser diode, but I'm assuming you need to do something with the little element at the top too before it works correctly.

    Any help/info/datasheets/thoughts, whatever, are appreciated

  2. #2
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    OK, I just did a little experimenting.

    I connected the module up to my Arduino's 3.3V pin. It can source a max of 200mA, so it's pretty safe for testing. I put the entire module ontop of a large TEC with a bit of thermal paste. When I connected the green module to power, it was emitting a smidge of green. I then connected the big TEC up to a 18650 battery, so the module was being cooled, and the green output quickly increased! It then started flickering off to the point where there was no output. Disconnected the TEC, and as its temperature headed back to room temp, the green light came back for a second or 2, then disappeared again. Reconnected the TEC and cooled it again, green light came back!

    So, it would appear that maybe the little "element" inside the module is a TEC? If so, what would be the best way to drive it, in terms of current? Last thing I want to do is feed it too much and POP

    EDIT: Got a video of my messing around with it. I'll link it here once it's done, but I think this is the first ever picture of one of these lasing outside the projector (by a hobbyist) ever



    Cheers,
    Dan
    Last edited by Things; 11-20-2011 at 07:18.

  3. #3
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    Dan,

    That little thing is a heater. Here is my guess on what is happening.

    You fire up the pump diode it warms the silicon plate that it is sitting on, you get a little green. When you cool the assembly down you are changing the pump wavelength slightly and your power goes up. then as it cools more you pass the wavelength match for the pump and dbr crystal then you loose lasing.

    I would attach the module to a heat sink so it can get rid of the pump heat. Then apply some power to the heater wires and slowly increase current until you get lasing back. Unless you have a good thermal controller for your tec it will just make things harder. I think that module is rated for about 60 or 70 mw so that is your goal.

    The way the pico projector handles this is they turn on the pump diode and set the heater some ware close then they use the photodiode that is mounted on the sled to look at green power and peak it from there. I think.
    When I looked at things on the scope they PWM modulate the heater current and you can see it PID hunt for the best light output.

    Congrats! As far as I know you are the first to get green out of one of those. I have one sitting here I just have been so busy that I have not had time to muck with it. But thanks you have confirmed the pin out conclusion that I came up with.

    *edit, if you look at the pic from "impulse" you can see the resistive element through the crystal. "The "M" looking thing.


    chad
    Last edited by chad; 11-20-2011 at 11:54.


    When the going gets weird, the weird turn pro.


  4. #4
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    Thumbs up

    Posting for tracking...

    ...But, 'long as I'm here, I'll take a stab...

    Quote Originally Posted by Things View Post
    ...I'm assuming you need to do something with the little element at the top too before it works correctly.
    EDIT, after reading Dr Chad's post, *not* an LED nor a sensor / part of an optical-feedback loop... Thx, Chad...

    Here's my best-guess, too, of what's goin down, optically...

    Click image for larger version. 

Name:	Picogreen_Optipath.jpg 
Views:	167 
Size:	198.1 KB 
ID:	28851 ..still can't quite make sense of the SHG path....maybe someone with a clue can fix my boo-boos?...

    ...fascinating stuff, this micro-module, eh?! Looking forward to the day when they miniaturize OPSLs... heh.. '..514nm OPSLs the size of pencil-erasers',

    Beam me up...
    cheers..
    j

    Ps - Sir Dan - see if you can get some '3/4 or side-view' shots from that LPF'er....
    Last edited by dsli_jon; 11-20-2011 at 14:08. Reason: read Dr Chad post...
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  5. #5
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    Cool, thanks guys!

    I know a PID library actually exists for the Arduino, and I have a few DAC's laying around, so I might try an optical regulation system at some stage as well.

    It is indeed a really cool little module, the fact you can squeeze 60mW+ out of it is quite amazing!

    Though, I can't really find any datasheets on the current ratings for the little heater and the pump diode.

    I've been powering the pump diode from 220mA ish, though I have a feeling that's a bit low & I have a lot more headroom yet

    Is there any way I can try estimate the max input current for the diode? The heater seems fine running off an Arduino output - limited to about 20mA or so.

    EDIT: Just thought I'd also add, I did have a suspicion of the "power hunt" regulation technique, since there is really no other way to regulate it. The crystal on the heater is actually very fast to respond. Infact, the output brightness of the thing almost followed the potentiometer by the second! If we do indeed get these running, but they won't work just setting the heater to a set level, might need to work out a way of "splitting" the beam and shooting some off to a photodiode and reverse engineering the "power hunt" method.

    EDIT EDIT: Jon, he's not a very regular poster, but he did post this:



    It's quite a beautiful picture actually.
    Last edited by Things; 11-20-2011 at 15:14.

  6. #6
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    Well, managed to get it stable for the first ever beam shot!





    It's soo cute!

  7. #7
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    Thumbs up

    Great werk, Dan!!

    ..And yes, that '3/4' shot is brilliant, thanks for the post... but, it raises as many questions in my mind about the SHG path / lateral-components, as it answers...

    Here's my 'revised guess'..

    Click image for larger version. 

Name:	Picogreen_Optipath_v2.jpg 
Views:	142 
Size:	198.9 KB 
ID:	28861

    ...Paging P'fessor Roberts! P'fessor Roberts?

    cheers..
    j
    Last edited by dsli_jon; 11-20-2011 at 17:25.
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  8. #8
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    It doesn't like running off the Arduino's power though, I need to build a proper LM317 driver for the diode.

    Can anyone give me a rough max current I should keep below? I had a 110mW green module that ran on about 1.2A, so if this module is 60mW, almost half of that, so around 500-600mA max maybe? Not really sure

    EDIT: Jon, your diagram looks pretty well right, except I don't think that block is a photo diode, rather just a vertical support for the HR mirror. There are photo diodes in the optical assembly externally
    Last edited by Things; 11-20-2011 at 17:46.

  9. #9
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    Yep looks good!

    I have some ideas for you.

    1. Use a smaller heat sink. Let it get warmer. don't be afraid of 85-90f or so. These get warm when running and I guarantee they took that into consideration when designing it.

    2. Set your current to 300mw for now. Set it and leave it there. Now you can play with current to the heater and see what gives you the most power out. I suspect it will be a range that works. If your porridge is just the right temperature you will get the most green out.
    This all about thermal stuff. The pump diode is going to shift wavelength with the temperature of the base of the module then you need to tune the crystal thermally to match *exactly* the pump wavelength. If the base of the module heats or cools then the crystal temp has to change to keep the optimal output.
    Remember that this is a battery powered thing so this is going to be the most efficient way of making green there is, minus a direct diode. What I am getting at is don't use typical dpss powers to guess at mw levels. These will be more efficient 600 mw would probably bake it.

    3. While you are building a constant current source, build two. Use one for the diode drive and the other for the heater. The heater is just a resistor so get your meeter out and measure the resistance of it. You can then use ohms law and a couple of resistors and a pot and play with temp for the crystal. Start at maybe 50mw for the heater max and see how things go, adjust accordingly.

    Once you have a good idea of what kind of power you get out of a fixed diode drive at 300mw and a stable base (warm)temp, then variable current through the heater you can inch up the diode current and play with heater temp and shoot for ~60 mw or so.
    Then you can build a smarter driver.

    Any way, this is basically what I was planning on doing, if I ever had the time.

    Good Luck!
    chad

    P.s. That is a beautiful pic. And some beautiful engineering and manufacturing. That thing is much smaller than it looks.
    Last edited by chad; 11-20-2011 at 17:54.


    When the going gets weird, the weird turn pro.


  10. #10
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    Yeah Chad, was intending on building some constant current drivers, just needed a current range to aim for! Maybe I'll grab a few resistors. Start off at 300mA like you said, and slowly crank it up.

    And yes, the heat thing has had me thinking. If we cool the module itself and keep it at a constant temp, then we should be able to do away with the optical regulation, and just tune the heater.

    From what I've already tried, it seems to be pretty stable, but my way of driving it is far from ideal. I don't have a clue on what current I was pumping the diode and heater with, and it has a long way to go before it hits 60mW.

    If it's gonna heat up a lot, optical stabilization might be the only way to do. Maybe be able to use one of the optics out of the assy as a "beam splitter" of sorts.

    Thanks for the tips.

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