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How to determine if a semiconductor laser is broken

  1. Aug 30, 2013 #1

    I was wondering if someone could tell me what the best way would be to determine if a semiconductor laser is broken using a multimeter?

    I have a semiconductgor laser that is still emitting but the signal appears lower than expected and it is hard to tell if it is broken internally. Does anyone know what the common problems would be?

  2. jcsd
  3. Aug 30, 2013 #2


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    With a multimeter, you can check if the electric properties (mainly the V/I curve) are still the same. Be careful if the laser has no electronics to manage the current, in that case your measurements can break the laser.

    Can you measure the laser intensity directly?
  4. Sep 2, 2013 #3
    Hi, I am getting some light out and I guess measuring the LI properties would allow me to clearly see if my source is lasing or not. I was wondering though if there were some typical faults that could be used to determine quickly and with some confidence if the laser had be damaged, e.g. measuring a protection diode or something.

    Do you know what the most typical faults would be?

  5. Sep 3, 2013 #4


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    you are not giving us much to go on
    how about a model of the laser module ( diode) ...
    do have a pic of it? do you have a link to some data for it ?

    playing 20 questions isn't really much fun :wink:

  6. Sep 3, 2013 #5


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    Try "Sam's Laser FAQ"; Sam has compiled an immense knowledge base for understanding and the repair of lasers.

  7. Sep 3, 2013 #6


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    If you have access to a spectrometer or monochromator you can check the emission spectrum. The lasing mode(s) is/are usually very narrow, while spontaneous emission is broad.

    In my personal experience the most common way to kill a laser diode is the combination of an undergrad student with static discharge. Besides that, it is hard to guess the reason without having more details.
  8. Sep 4, 2013 #7
    Thanks for your comments everyone.

    I am quite sure the laser is broken. I sort of already knew this as the spectrum, as seen on an OSA, is weak and not particularly sharp. The problem is that if I do this measurement I could also suspect that the drive circuit is faulty and not delivering the correct conditions for the laser to lase. Really what i was attempting to find out here was if there were common faults, generally speaking, which could occur - perhaps because of handling or excesses drive currents/ high voltages which could be easily identified through the simple use of a multimeter. Perhaps static discharge is this, but if so, can I determine this with a multimeter and know with some certainty that the fault is with the laser?

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