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Thread: CNI linearity issues.

  1. #1
    Join Date
    Dec 2009
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    Sydney, Australia
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    Default CNI linearity issues.

    Hey guys.

    Just got my meter up and running, using a coherent 210, and decided to do a linearity graph on my CNI MGL-III-400. , It's not calibrated yet, but I know it's pretty close, and the graph just shows it referenced to the detected full power. When I'd connected it up to a pot and twisted it around, I'd noticed the obvious bumps and power drops at two points. The graphs ended up showing this:

    Click image for larger version. 

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    Red was at startup, green was about half an hour after.

    Is this a major flaw? Something that I can fix? Or is it normal?

    Thanks guys.

  2. #2
    Join Date
    Nov 2005
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    Melbourne, Australia
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    Default

    Thats pretty typical on most Chinese lasers from all manufacturers. Some are worse than others.

    Once you are scanning, the dip wont be a issue at all.
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  3. #3
    Join Date
    Dec 2009
    Location
    Sydney, Australia
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    Default

    Is it that the dip actually goes away when modulating? Or just that you won't notice it.

    Thanks.

  4. #4
    Join Date
    Jul 2005
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    Default

    Don't you just love DPSS technology? Thermal issues with SHG crystal...normal...for most like Dave said. Not to worry...direct 523nm diodes are being evaluated in China. You would hate to see the actual bumps with a photo diode and fast modulation.....did someone say picket fence?
    You are the only one that can make your dreams come true....and the only one that can stop them...A.M. Dietrich

  5. #5
    Join Date
    Dec 2009
    Location
    Sydney, Australia
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    Default

    Picket fence as in my power response? :P

    The diode current is constant across the range of modulation, that isn't a problem.

    I probed around the psu a bit today, trying to find anything to do with photofeedback. Not much luck.

    Anything I can do in terms of TEC adjustment, or max diode current, do get the gradient a little bit less... well, less looking like a mountain range? I can easily sacrifice some power for my planned projector setup.

    Thanks again.
    Last edited by aXit; 08-09-2010 at 06:08.

  6. #6
    Join Date
    Nov 2005
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    Default

    I wouldnt worry too much TBH.. Maybe it would be a bigger issue if you have a pair of these lasers, and are trying to get matched yellows and cyans, etc
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