They kind of look like they're hollowed out but show no signs of being seamed together.
You take a few lasers pointed in from different angles and have them cross at a single point. Individually they don't have enough power to damage the material but they do when you cross multiple beams
That's very interesting. Thanks!
This is also the same principle used in radiology for treating cancer.
And in laser eye surgery iirc.
Hmm I would have thought they were a special kind of laser:
ultrafast lasers, or femtosecond lasers.
They have extremely short pulses with huge amounts of peak power. Unlike 'normal' lasers that machine or mill material away by boiling and vaporising, these lasers machine or mill by 'cold ablation': the huge light field power frees the electrons, then it becomes opaque, so absorbs more light, so it frees more electrons, then it becomes more opaque etc etc. Eventually there is no more electrons holding the material together, and it just explodes.
It's just that it happens in a tiny scale; if you look at it with a microscope, it's an absolute mess.
In theory, crossing multiple laser beams sort of seem plausible, but glass is transparent! a few times more powerful light generally doesn't make a difference. Nanosecond lasers are often used for metal machining. Peak power wise, femtosecond pulses can be 1000000 times more powerful...
They're called sub-surface laser engravings or bubblegrams. When doing laser engraving, typically they focus the laser on the surface of the material. It creates a microscopic fracture. With glass, crystal, and certain plastics, you can focus the laser below the surface. This causes the microfracture to occur deep within the glass itself, not just at the surface. By adjusting the focus depth, as well as the X and Y coordinates of the laser, a 3D engraving can be made.
Block* I meant block
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