How to make the etching in the middle of the acrylic?

You know in the mall where you see the kiosks that puts someones photo etched into a THICK piece of acrylic (or glass?) but it’s in the center of it not on the surface… How is that done?


It is done with a different kind of laser.
The light emitted by a CO2 laser (like a Glowforge) is absorbed at the surface of the glass, but other kinds of lasers are able to focus in the middle and create tiny pits.

We actually had a discussion about this a while back, but it was under a different topic:


Ohhh! There ya go. I just didn’t know what to look for. Thanks @jkopel

Of course there is always another way…
If you want that effect you could cut a bunch of glass pieces, engrave them with successive layers of an image, and then stack the glass using an optically clear adhesive (or maybe fuse them in a kiln?).
Sort of like:

( )


Two-photons. Each photon doesn’t have enough power to etch independently, but where the beams combine the magic happens. Same principle is used in microscopy for visualizing fluorescent markers deep inside tissues without background noise.

If you want to build a two-photon microscope (or laser engraver) theres an OSHW project for that!