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I have come across a project which used this Chinese laser module. Apparently from someone who worked with the mentioned laser, it emits IR light (noise) even though it's a green laser. While I was browsing for alternatives on Digikey, I have a hard time finding an alternative that has an IR filter built in to get rid of the noise. Here are my questions.

  1. From your experiences working with the laser modules ordered from Digikey, have you encountered any issues with IR noise?
  2. Should I be looking at lasers with similar wattage to ensure similar brightness?

Thanks in advance for your help!

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Chemistry dictates that lasers often produce light in the infrared spectrum. Popular neodymium-doped lasers produce light at 1064 nm, which is well into the infrared range. To get around this, frequency doublers are employed, which halve the wavelength to 532 nm, which is a green light.

For this reason, it's unsurprising that your laser emits IR light. The frequency doublers aren't perfect; a significant amount of IR gets through. Good lasers will filter this out, cheap ones won't bother. If this is important to you, use a reputable manufacturer (like the ones on Digikey) and verify that they at least claim to use IR filters.

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I have 2 green lasers from DX, and both are without IR filter.

Personally, I don't think it's a problem as IR is way less collimated, so at a distance, only green dot is in focus.

Extra IR filter would reduce usable output power & will increase it's cost.

If it's critical to you - you can pass your beam through prism, so that 532nm beam would be split from 808nm/1064nm IR light, then you can put an obstacle on the path of IR beams.

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  • \$\begingroup\$ I wouldn't recommend using a prism, that will direct a beam of invisible, high-power IR light in an unknown direction. If you don't want a filter, it's much better to have it in line with the green light, so you can avoid pointing it into people's eyes. A filter will block the IR as opposed to diffracting it; a good one won't block much more than a glass prism would. \$\endgroup\$ – Kevin Vermeer Apr 6 '11 at 13:35
  • \$\begingroup\$ I wasn't meaning to allow this IR beam to just fly somewhere :-) You can see it with webcam, and block it reliably. \$\endgroup\$ – BarsMonster Apr 6 '11 at 15:44
  • \$\begingroup\$ +1 for unique use of a prism. You could pass the beam through an aperture further on to block out anything that got split off (assuming they were refracted at a significant angle) \$\endgroup\$ – pfyon Apr 6 '11 at 16:32

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