Can someone explain to me technically what’s going on here? Is not burning the top but yes the bottom? WTH
The acrylic has a very high transmission rate at the lasers wavelength, so it doesn’t absorb any energy. The wood blocks all wavelengths, so absorbs the laser energy, burning it.
The principle is the reason a k40 doesn’t destroy it’s own lens, even though it has very poor wideband transmission (so looks nearly opaque) at many wavelengths, it has a very high transmission rate at 10,8 micron.
I’m not 100% up on the molecular physics involved, but it’s sort of like a screen which gravel will pass through, and you dump a bucket full sand thru and it has little effect, but if you dump in a bucket full of rocks, it tears the screen right out of the frame. Think of the acrylic in the video as haveing sub molecular holes in it which let the short wavelength violet or blue light thru. If you hit the same piece of acrylic with the longer IR from a CO2 laser, it will be absorbed and vaporize the acrylic.
It’s not really that simple, but the real explanation makes my head hurt…
Scott
I take it you are using a laser diode?
This isn’t 10600 nm is it? 445 nm laser diode? Its transparent …
yes, the acrylic, should have its opaque adhesive protectant layer
on it so the laser doesnt pass through it.
Ok so keeping the protective layer make sense but as I need multiple passes to cut it it will not help in the long run.
I guess this is the same reason that not all laser goggles are suitable for all types of laser wavelength. Interesting to see it actually in action, so thanks for sharing Ariel 
@Yuusuf_Sallahuddin_Y it was like a nightmare / magic trick
@Yuusuf_Sallahuddin_Y
Much more elegant way of putting it.!
The graph from @donkjr shows, that normal Plexiglas (Acrylic) should be a good eye protection for CO2 Laser 