[SGVHAK] Laser Safety

[James McDuffie]

I've talked with a couple people recently about laser safety. Especially
troubling to me is the fact that some visible laser diodes have
resonances in the IR wavelength range. For instances, the following
article talks about how cheap Chinese manufactured green laser diodes
were emitting excessive amounts of IR. Sometimes more IR than visible
light!

http://www.technologyreview.com/view/420214/the-danger-of-green-laser-pointers/

A good way to check this is to use a CDROM as a diffraction grating and
then photograph it with a camera sensitive to IR light. The problem is
due to the fact that laser diodes have resonance emissions and many of
the cheaper diodes have no IR filtering. 

This link also has some more safety tips related to people using DVD
laser diodes:

http://www.laserist.org/DVD-laser-caution.htm

Now you'd think, I will just buy laser protective goggles. That might
not be enough. You might buy goggles that cover the wavelength range in
the laser diodes's spec, but there will still be spurious out of band
emissions. One source told me that the laser protective goggles use very
narrow band filters. So if it doesn't list protection in certain
wavelength range you should assume it is transparent to other
wavelengths.

Now you might say, as I did, what about those commercial laser cutters
that have a large window on top and apparently a simple protective film.
Well, these are industrial products and their lasers are most likely
crystal based and not using cheaper diode lasers. They are tuned and
tested for a narrow wave length range. That is part of their expensive
price tags.

So what could happen? Well with visible and near IR wavelengths you
could damage your retina. For IR and above, even though your eye lens is
opaque to it, the radiation can damage your outer lens and cause
cataracts. 

Not all lasers are completely dangerous, the class 3 and 4 ones are what
you have to worry about:

http://www.ipgphotonics.com/company_service_safety.htm

tldr: Be extra careful with higher power lasers you have pulled out of
equipment or bought off eBay.

<insert "the more you know" rainbow here>