Some folks I used to work with at NIST have looked at cheap green laser pointers, and found a potential danger. Some of the dimmer-looking green lasers are not so dim in the infrared, and in one case emitted 10X the rated power in invisible light. This could be a potential eye hazard.

You can read their full report on the arxiv. It’s got a nice description of how green laser pointers turn infrared light into visible light, which is really pretty awesome– a guy I met at a conference once declared them the coolest invention ever, because it’s “quantum optics in the palm of your hand.” Better yet, it describes a cheap and easy experiment you can do to see if your green laser pointer is dangerous, using a CD and a webcam. And best of all, it demonstrates a clear understanding of what these are really used for:

Note that the infrared spots [in a diffraction pattern] exhibit greater divergence than the green. The infrared light spreads out beyond the green, which could be injurious, for example, to a cat closely chasing a spot of green light.

So, if your green laser doesn’t have the oomph you would like it to have, it might be because you’re looking at the wrong wavelength. So avoid shining it into your cat’s eyes until you get a chance to do their experiment and check it out.

Comments

  1. #1 Jake B
    August 14, 2010

    Hope you don’t mind I linked back to your entry here.

    This is especially poignant to some military people I know (if only they were reading my blog) since a great many have bought their own green laser pointers and using them if they didn’t get issued one as a warning device.

  2. #2 anders
    August 15, 2010

    you probably knew this already, but instead of that 100$ fluorescent card from Thorlabs or Newport your cell-phone camera with a large live-view screen works quite well as an IR-detector. At least for 1064nm and 808nm which is what comes out of the 532nm pointers I guess.
    The surface of a CD or a DVD could probably be used as an el-cheapo diffraction grating…

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