Laser ir leak?

So i have this cheap ebay laser from ebay.com
It came from hong kong

I have heard alot about ir leakage?
What is it and how can it damage you?
and is there a way i can test how much ir my laser pointer leaks?

-Fojumdk

IR is present in many lasers, I assume you have 532 nm - green - there is IR involved from 808 nm pump laser diode and 1064 nm from Nd:YAG (typically) crystal - solid state laser which us pumped by 808 nm. There is also another crystal making 532 nm green from 1064 nm. 808 and 1064 both are considered as IR. If not filtered they might be dangerous as these are invisible and you do not get reference of painful bright light to blink - you will not notice there is something wrong untill it is too late. Be aware as IR might not be colimated as visible output radiation. Also pump laser diode (808) is much stronger than output green due to efficiency issues... You can see if there is a leakage by letting laser hit some diffraction grating like cd or dvd and observe interference patterns - dots laser creates on wall after reflection from disc. Use not IR filtered camera and compare if there are additional dots from what you see with your eye - if so there is no or insuffiecient ir filter. BTW use proper laser safety glasses for this experiment - cheap lasers might be overpowered even if rated 5 mW and under.

fojumdk said:

I have heard alot about ir leakage?
What is it and how can it damage you?

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532nm lasers (cheap green ones) use a technology called DPSS (diode-pumped solid state). The laser diode that pumps the solid state (crystal) part of your laser produces quite a lot of 808nm IR light. Some of this gets converted into another IR wavelength by one crystal (usually Nd:YAG), and some of that gets converted into the 532nm green light by another (KTP).

Depending upon how well the laser was made, this IR can escape the laser in large amounts, especially if they lack the IR filter common on most high-end DPSS lasers.

What ends up happening with cheap lasers is that you have basically a green laser beam with a dot in the middle of what's essentially a wider "flashlight" of bright IR light. The IR isn't good for your eyes, and it's hard to know if it's hitting them since it's very hard if not impossible for most people to see. It reflects better than visible light off of some surfaces, and shining the beam in the direction of anybody's face is risky (not that you should do that anyway).

All that said, the IR is more diffuse than the green light, so it poses a bit less of a hazard when handled carefully.

The IR leakage isn't found in any other common wavelength of affordable hobbyist laser unless you consider the yellows affordable.

fojumdk said:

and is there a way i can test how much ir my laser pointer leaks?

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Filters and spectrometers are the most surefire way to tell, but some cameras can sometimes pick the IR up if the laser light is obscured.

Depending upon how good the green beam is, I've put a hole in a sheet of paper and shined beams through it to see the halo of IR on the paper.

EDIT: Radim's test method is better, but please don't attempt something like it without laser safety glasses for your laser.