Beam blocks

[Arayan]

I wanted to ask if any of you use some material suitable for blocking unwanted scattered radiation from high power laser (for example CO2 or near infrared, 808nm of differente watts). I found some "beam traps" (for example at thorlabs.com Thorlabs.com - Beam Blocks, Traps and Shutters) but they are expensive and often not availables for international shipments.
Is it possible to find more cheap material which can perform similar functions?

Thanks

 

[phoenix77]

Get an IR filter, for the 808nm. Check out websites like OEM LASER SYSTEMS, MAXON TECHNOLOGIES, Etc. They sell LASER SAFETY GOGGLES, & LASER SHIELDS for different wavelength lasers.................rob

 

[Meatball]

I use small "blocks" of wood as my backdrop...

 

[Arayan]

I use small "blocks" of wood as my backdrop..

yes, but I know that for the CO2 laser also the wood can have a good reflection... then burns I had thought somethin in graphite but it is not easy to find (except the one for pencils but it is not exactly suitable)

 

[Asherz]

Block o' concrete or a brick?

 

[Arayan]

Yes I need a block that blocks and can be also be a brick ... but black

 

[Benm]

It needs to be 'black' at the wavelength you are working with. For CO2, i've seem people use cinderblocks as beamstops - at higher power levels a red hot area will develop at the impact point.

For visible lasers a anodized black heatsink works fine. It's not a real beam trap, but most of the light ends up absorbed, and if its matte, the rest scattered. You should be careful with glossy black surfaces though - especially at shallow impact angles they can reflect quite a bit of light even though they appear pretty dark black when you just look at them.

 

[Arayan]

Thank you for the response, hence you say that the reflection from the cinderblocks, for CO2 lasers, is low?

 

[RA_pierce]

For visible lasers a anodized black heatsink works fine. It's not a real beam trap, but most of the light ends up absorbed, and if its matte, the rest scattered. You should be careful with glossy black surfaces though - especially at shallow impact angles they can reflect quite a bit of light even though they appear pretty dark black when you just look at them.

Anodized aluminum reflects near IR.

For my >2W 808nm (and my various visible wavelength lasers) I use a slab of stone spray-painted matte black. With the 2W, however, the painted surface will burn if the power density is too high.

10.6µm is absorbed by many surfaces including materials that are transparent to visible light, but like others have said, a cinderblock or brick should work well.

 

[Arayan]

10.6µm is absorbed by many surfaces including materials that are transparent to visible light, but like others have said, a cinderblock or brick should work well.

Therefore a CO2 laser used in a room with "rough walls" does not need any beam block.

 

[Benm]

Depends on if you actually like the wallpaper or paint... A powerful CO2 will defintely burn a hole through paint or paper, and the latter could even catch fire. Something like a cinderblock can be heated up until it literally glows red hot without ill effect.

As for black paint for visible lasers: it will indeed work well up to a certain power density level. If you focus a few 100 mW to a pinprick it'll burn the black paint on/off any surface, even metal.

Anodized layers are thermally conductive themselves limiting this problem, but they could indeed be reflective in the near-IR. There really is no way to make sure other than to test it - near-IR (or visible) albedo is not important for the function of any heatsink.

The fact that most are dyed black is more for historical/esthetical reasons than for performance. The only thing that matters is the albedo in the far-IR, as it is only there thermal radiation occurs at room temperature or slighly above.