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Thread: 660nm and 405nm laser diode output comparisons

  1. #1
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    Default 660nm and 405nm laser diode output comparisons

    In the quest for inexpensive but ever more powerful lasers, and more exotic colors, I have had the opportunity to test many diode makes and models. In doing so, and after several lifetime tests there are a few things that have become clear that aid in determining maximum safe operating current of the lasers. First off, the die length of the diode resonator is related to its maximum output power, voltage drop, and lasing threshold. Longer die diodes typically have a higher lasing threshold, lower voltage drop, and a higher sustainable maximum current before entering dangerous territory. In the current ramp plot of a diode, you will see a smooth ramp after the lasing threshold has been reached, eventually followed by dips and bumps that indicate you are driving the diode past its safe long-term operating point. TEC cooling can extend the smooth ramp range somewhat, but there are hard limits that even cooling cannot overcome.

    All tests were performed at room temperature 21-25C using aixiz modues with multi-element glass lenses for the red diodes and aperture-opened plastic lenses for the 405nm diodes. Plastic lenses were used for 405nm because the AR coating of the glass lenses tended to decrease output. All diodes were 5.6mm mount packages.





    The current winners are the LG GGW-H20L in the 405nm camp with its laser etched bar code on its back, followed by the old xbox 360 hd-dvd add on drive laser (phr-803t pickup) of the same manufacturer. In the red camp, the Long-die open can diode from the sony NEC opticarc 20x dvd burners and Pioneer 112D, 115D burner. These diodes have been tested for weeks continuously at over 200mW and currently represent the best available 658-660nm diode tech in 5.6mm mounts.
    Last edited by drlava; 05-12-2008 at 21:06.

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    Thanks for that ! Just one question. What voltages were you running them at?

    Chad


    When the going gets weird, the weird turn pro.


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    umm, laser diodes are current driven ...

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    Yes they are, but...

    I guess I will just run them at 0 volts then.

    Take a look here :
    http://en.wikipedia.org/wiki/Diode

    and read the section: Current-Voltage Characteristic

    chad


    When the going gets weird, the weird turn pro.


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    Good question chad, I do have all of the voltage plots for them also (V-I). The red lasers operated at about 3V, the lower lasing threshold diodes climbed in voltage faster than the diodes with higher lasing threshold, again due to the die length.

    The blue diodes operated at about 4.8V with the same properties.

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    Quote Originally Posted by chad View Post
    Yes they are, but...

    I guess I will just run them at 0 volts then.

    Take a look here :
    http://en.wikipedia.org/wiki/Diode

    and read the section: Current-Voltage Characteristic

    chad
    I know how diodes work.
    I just meant to say that the voltage they're driven at does not matter, since it is the current you should regulate.

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    Yes, you do regulate the current. But you need to know the operating voltage so you can size your PSU accordingly. You're not going to run a blue ray diode off a 3 volt power supply, for example. Chad's question was a reasonable one.

    Adam

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    Talking

    I'm so glad that some people are willing to put a lot of time, effort and expertise into stuff like this and share the results!

    I don't know Jack about SS lasers (I don't know much about ANY kind for that matter). Someday soon I'd like to get an SS projector of my own. Information like this is priceless!

    Thanks!

    James.

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    HI,

    Listen I am not trying to get into a pissing contest here but I look at this board as a great educational resource and as such I don't want to see misinformation spread.

    "I know how diodes work.
    I just meant to say that the voltage they're driven at does not matter, since it is the current you should regulate."

    Led's are pretty forgiving when it comes to voltages but Laser diodes are very picky about voltages and can be blasted easily.

    Dr.Lava's charts are a great reference. He put a lot of time into them and they contain great baseline measurements. However without the voltages on the chart the current measurement is totally useless and has no meaning whatsoever. Ohms law still applies.

    This is the reason that I asked about what voltages he ran them at. led's and Laser diodes current can change drastically with a very small change in voltage.

    Red and green diodes will emit at lower voltages than a blue or white. In this case voltage very much does matter. If you give a nuv Laser (405nm) 1.5v no matter how much current is AVAILABLE to it, it will not lase.
    Current and voltage and resistance are intrinsically linked, you can not have one without the others.

    Because you 'know how diodes work' this is more of a quick and dirty FYI for people who are newer to this stuff.

    Chad


    When the going gets weird, the weird turn pro.


  10. #10
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    Quote Originally Posted by chad View Post
    However without the voltages on the chart the current measurement is totally useless and has no meaning whatsoever. Ohms law still applies.
    No meaning? many people on LPF setting their current drivers beg to differ. It's important to know the approximate voltage required to drive the diodes, but as has been said, since you're not using a voltage mode regulator to drive the diodes if you're sane, the current level is the most important. Also, being the x-axiz of this chart, the current wasn't measured - it was set, or prescribed for each data point.

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