
What Is Sub-Surface Laser Engraving or a 'Bubblegram'? Technology Explained - peter_d_sherman
https://www.youtube.com/watch?v=sOrby692Uag
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peter_d_sherman
Excerpt from Thom1218's comments on YouTube:

"The lasers in these machines HAVE to be pulsed, using a method called
Q-switching to obtain high peak-power pulses that can couple their energy into
otherwise transparent material. These pulses, incidentally, are in the
megawatt range and over a very short time span, usually a number of nano
seconds. These lasers use several IR diode lasers to "pump" a Nd:YAG laser
crystal, which is frequency doubled from 1024nm to 532nm (green) in order to
be able to pass into the glass target object. Interestingly, this laser
technique is used in tattoo removal machines to penetrate skin and oblate sub
dermal ink . CO2 lasers can do a continuous etch on glass because glass is
opaque to the near IR long wavelength of CO2 lasers, and therefore they can
only etch the surface. Also, because glass is opaque to CO2, more energy is
transferred directly to the glass, rather than passing through it, which
allows the CO2 laser to remain in CW operation (continuous wave, i.e. not
Q-switched). So, the operators of these bubblegram machines do not have the
option to do a "continuous blast". However, using fewer dots/bubblegram will
shorten processing time and wear on the laser components."

My thoughts: Absolutely fascinating!

Also, I wonder if it would be possible to condition glass in some way to act
as a transistor, whether optical, electrical, or for some other particle/wave
phenomena. Like maybe lead glass, or other glass which contains metal
particles in it -- would change its waveguide properties at points where a
laser etched it... thus, maybe it might be possible to etch some kind of
transistor (for a specific wavelength/wave phenomena) into it...

