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Etching Plastics? Long!


#1
    A laser is essentially a machine which takes electrical and
electromagnetic energy and converts it to a beam of energy.  Lasers
are defined by the type of material used to generate the energy, in
this case Carbon Dioxide or CO2.  

G’day; I hope you don’t mind my poking my nose in here and meddling,
but couldn’t resist it. The statement above is perfectly correct, but
I would like to expand it a little. (The joy of written words is that
you can always skip them if it gets boring).

The ‘beam of energy’ produced by a laser can be more easily regarded
as a very narrow and highly concentrated beam of electromagnetic
radiation of which ordinary light is an example. The fact that all
the waves of laser ‘light’ are coherent - that is, in step - is a
little irrelevant to what a jeweller wants to know about it. Light
emitted by a laser has a very narrow beam which is almost completely
parallel; it doesn’t spread out much at all. The CO2 laser produces
light invisible to the human eye; that is, infra red radiation which
we can only sense as heat.

Now, when light strikes an object, some is reflected - which is why
we see it. But some is also absorbed by the object, especially if it
is black. Black velvet, for instance reflects practically no light -
probably less than 1% of the light falling on it. Because
energy/matter cannot be created or destroyed; only transformed from
one form to another, the energy in the light beam has to go somewhere,
so the absorbed light becomes heat, and the place where the light
strikes becomes hotter. If the beam of visible light is very
powerful and very highly concentrated, that tiny spot becomes hot
enough to melt metals, and infra red light produced from a CO2 laser
is more easily absorbed by some materials (such as plastics) than
visible light.

Most metals only reflect a certain amount of the light radiation
falling on them. Silver is one of the most reflective, so needs a
particularly powerful laser to weld it. Gold reflects infra red rather
well, so a helium/neon or ruby laser can be used for this. Steel
absorbs most laser light quite well.

Radio by the way, is also a form of electromagnetic radiation, quite
similar to light though of course we can’t see it. So, can radio
waves act like light from a laser? Yes indeed; only radio lasers are
more properly called masers; Microwave Amplification by Stimulated
Emission Radiation. The others are, of course, Light Amplification by
Stimulated Emission Radiation. The satellite radios use masers.

Well, that was doubtless far more than you ever wanted to know, and
only slightly clearer than mud, but there it is for what it is worth.

Cheers now,
John Burgess; @John_Burgess2 of Mapua Nelson NZ