Thursday, October 25, 2007

Dangerous Green Laser Pointers

Posted on 2006-12-16. Permanent link:

Ref.: encyclopedia articles on laser pointers and laser safety

Here is a safety warning which might help to prevent terrible accidents. I just learned that some people are selling quite cheap "laser pointers" via ebay, emitting green light at a power level of the order of 100 mW. Such a power level is of course well above what is reasonable for a laser pointer – about 1 mW should normally be enough. (Less optical power is required for a green laser pointer, as compared to a red one, since the eye is significantly more sensitive to green light.) Indeed it is shown that such lasers can ignite a watch, burn skin, etc.

To make things worse, there are reports that such pointers sometimes even don't have a proper filter to remove the infrared light! Without a filter, there can be an infrared power of many hundreds of milliwatts, as the green light is not directly generated with a laser diode, but rather by frequency doubling the output of an infrared solid state laser (a kind of microchip laser) which itself is pumped with an infrared laser diode.

Even without the infrared light, such devices are rather dangerous: directly looking into the beam, you can destroy your eye within a fraction of a second. Even a weak reflection is strong enough to cause an injury of the retina.

I leave it to the readers to judge how responsible it is to sell such devices as "laser pointers", not even making people aware how hazardous they are.

Thanks to Russell Grew who made me aware of this.

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