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I'm building an enclosure for a laser engraver that emits light at ~455nm. I want to be able to measure the wavelength of the light that is refracting off the item being engraved. I would want to be able to measure an initial control with no protection. Then do additional measurements with different materials and colors.

I.e. comparing clear acryllic vs orange polycarbonate vs a green film.

Thanks for any input!

Philip Edwards
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    Also note that unless your material is unusual, and you're measuring the wavelength in air and not in some other medium, then the wavelength of the light should be the same in all cases (from the source, reflected, transmitted, etc.) – Michael Seifert Mar 07 '22 at 16:42
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    Of course, that wavelength could excite fluorescence in some materials. – Ed V Mar 07 '22 at 16:48
  • I have seen the method for using grating and measuring the distance between. Which could be a solution if I decide to emit the laser directly through the material instead of attempting to measure the light that refarcting off of the item being engraved. – Philip Edwards Mar 07 '22 at 16:49
  • What I'm challenging is I have seen claims where people opt out of buying "Laser Protection Acrylic" and buying just simple orange or green acrylic. The claim being that since the acrylic is orange or green, it blocks blue light. – Philip Edwards Mar 07 '22 at 16:50
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    This is an important clarification. An obvious thing to do is simply get some orange or green acrylic, like you might use in an enclosure, and then test it to see if it blocks 455 nm light reflected off a shiny surface. Of course, you should absolutely also be wearing proper approved safety eye protection, even for any preliminary testing. – Ed V Mar 07 '22 at 17:38
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    I don't think you want to know the wavelength of a laser beam at all, but the intensity - in which case you'll want a laser power meter (entry level price around $200 US) or possibly a regular light meter (entry level price around 40 USD) if you're measuring a scattered source like reflection off of the laser target. The laser wavelength isn't going to change. – g s Mar 07 '22 at 17:42
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    Much appreciated and glad to have helped a bit! – Ed V Mar 07 '22 at 18:25
  • You guys are spot on. Now I see that I was approaching this wrong. I'm not sure where I got to the conclusion that the wavelengths would change vs just simply being blocked. – Philip Edwards Mar 07 '22 at 18:26
  • Thank you @gs for providing me with insight for what I might need to measure the intensity. – Philip Edwards Mar 07 '22 at 18:28
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    I'll now do some research into what an acceptable amount of intensity would be. Ultimately I want to compare reputable laser protection rated for my nm against less reputable and acrylics not at all marketed for it. – Philip Edwards Mar 07 '22 at 18:30

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I do not have a 455 nm laser, but I do have a 405 nm laser pointer. Here is what happens when light from that laser pointer strikes a large uranium glass cube:

Uranium glass cube and 405 nm laser

As you can see, the uranium glass fluoresces green and the incident light intensity decreases significantly. But some of the 405 nm light makes it through the uranium glass cube, despite its thickness.

Now here I have placed a UV blocking piece of orange plastic between the laser and the uranium glass cube:

Blocking the 405 nm light

The orange plastic filter fluoresces yellow and it blocks essentially all the 405 nm light from the laser. The uranium glass cube does not fluoresce, indicating negligible 405 nm light got to it through the orange filter, and I tested with all the lights out. So the thin orange plastic did what it was supposed to do.

Bottom line: color of the acrylic plastic alone is not sufficient to risk your irreplaceable eye sight on.

Ed V
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