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Thread: DVD diode life

  1. #1

    Default DVD diode life

    I recently finished my second DIY red pointer. More here, with pictures:
    http://www.laserpointerforums.com/fo...num=1199862174

    I'm using the Sony 16x DVD diode, 5mm can. These are are specced around 80mW CW (@ 130 mA). However most people making these into pointers drive them with between 200-300 mA (or more) of current. These Sony diodes are usually good for around 200 mW @ 300 mA.. I'm running mine @240 mA which should put the power ~150-170 mW.

    My question is how long these devices last when driven this far over specifications? I know there are many variables, including the heatsink and the duty cycle.

    Assuming a decent heatsink and light duty cycle (just a few minutes on time) how long will these diodes usually last?

    It would be interesting if someone would graph the time to failure for a diode at different current levels. Say 1 minute on, 1 minute off until death. I figure for a pointer even a few 10's of hours is a long life.

  2. #2
    Join Date
    Oct 2006
    Location
    Cleveland, Ohio
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    2,332

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    If you can send 10 diodes, I could run this test on my automated rig, and I'd return them when finished .
    BUT, my guess is, when you are overdriving them this much, with a life length of hours, the final T.O.D. is largely variable from one diode or batch of diodes to the next. Also, it would be much more sensitive to temperature and turn-on speed, which are things that are rarely controlled by hobbyists.

  3. #3
    Join Date
    Feb 2007
    Location
    Herts, UK
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    Nice idea FloggedSynapse

    Problem is that the minimal "overdrive" testing I have done also backs up drlava's comments about variation between examples.

    I found marked EOL inconsistencies when pushing them over a certain current that would make accurate predictions impossible, and that was with the temp and duty cycle variables removed.

    Admittedly, that is one manu, and I didn't run these for 1,000's of hours either.

  4. #4

    Default

    It doesn't surprise me it's hard to predict.

    I seem to recall reading in SAM's faq that it's the number of crystal defects in the diode that determine its overall life. If you get lucky and get one with very few defects it may have a long life even driven overspec. Then that would be about as reliable as winning the lottery.

    Just don't know enough about laser diodes to say. It's very hard to find any single mode diodes > 150 mW. I know a lot of the early problems with developing high power laser diodes revolved around preventing COD to the end facets. One of the many secrets of the trade. I wonder what the limiting factors are to producing higher power single mode LDs.. I'm certain the demand is there if someone could figure out a way.

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