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Thread: Operating CW laser diode in pulsed mode

  1. #1
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    Default Operating CW laser diode in pulsed mode

    Anyone have any references to the max peak current that can be applied to a high power CW LD (1W 445nm) if the average current is kept to the rated value? I can't find much via Google.

  2. #2
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    How short of a pulse are you planning to use? If you keep the duty cycle low they should be fine up to about 2A, but I would not push it any further. There will be a diode lifetime vs current tradeoff, which I don't think anyone has published for these diodes (the whole not being actual products doesn't help, but even for nichia diodes there is no pulsed data that I have seen), so if you do not want to characterize it you should keep the pulses current below the safe CW current.

  3. #3
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    Somewhere around 250uS. 25% duty cycle. It's my understanding that damage to the facet is caused by high average power. I thinking of running a test where I applied a 25% duty cycle at 1kHZ. I would raise the current while watching the average power and see where it starts to "knee" at. I could then compare that to the CW PI curve. Or maybe set up a series of 250uS one shots and raise the power while watching the output with a PIN diode. Not sure how to find the lifetime trade off. Is it as simple as running the setup for 10hr and then 100hrs and measuring the degradation in Pout as one would do with a LED?



    Quote Originally Posted by krazer View Post
    How short of a pulse are you planning to use? If you keep the duty cycle low they should be fine up to about 2A, but I would not push it any further. There will be a diode lifetime vs current tradeoff, which I don't think anyone has published for these diodes (the whole not being actual products doesn't help, but even for nichia diodes there is no pulsed data that I have seen), so if you do not want to characterize it you should keep the pulses current below the safe CW current.
    Last edited by logsquared; 12-16-2012 at 09:13.

  4. #4
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    These diodes are designed for CW as opposed to QCW or pulsed. These lasers have an extremely low thermal inertia as well as extremely high irradiance on the facets (again because of their small size). I can't find it yet, but there was a blurb about a year ago about a 1% duty cycle blue diode that produced approximately 100 x the average power which I believe was in the neighborhood of 1W. This was considered a big success and I will keep looking for it.

  5. #5
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    Thermal inertia seems to be a limiting factor. As well as localized heating around the bond wire attachments. It would follow that a lower duty cycle with higher peak power would be easier on the diode. Basically, giving the die more time to equalize temperature.

    I just can't seem to find any info on how to calculate or predict short or long term effects. I would love to see that paper if you can find it.

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