Re: [CAD_CAM_EDM_DRO] Re: Laser Project

> OK, Like I build one of those 55W CO2 Laser Kits (someone just posted
> the web page, and I didn't bookmark). and like later on... Could I
> add a second 55W Laser in parallel? And like a couple more next time?

Most big commercial lasers are called multiple bounce and they are a long
cavity that's been broken into sections and put side by side with each
other. One very simple way would be to just remove the end mirror of one of
the tube, replace it with a material that's transparent to IR and then have
the mirror used on the end of the newly added tube. Many of the optics
you'll buy for home brew CO2 laser kits will stand a few hundred watts of
output. The real money comes in when you are using kilowatts because then
the mirrors get warm and need little tiny channels cut into them to let
water flow through for cooling.

You could colminate them in a few ways. One would be to have them both line
up dead on with a focusing lens, so they're side by side tilting inwards,
with a diverging lens after it to make the beam leave in a parallel fashion
at the size you want it. That would mean making a stand to hold the lasers
steady while they were on so's not to let their angle with the lens change.

Places like Edmund Scientific sell a catalouge full of weird and wonderfully
shaped mirrors and lenses for beam shaping and colmination. All you need to
do is ask for a copy of the magazine to have a read through. And hurray for
them, they have put prices in it too!

> I can't visualize any way of optically coupling two or more beems
> exactly. One could get close by just hitting the same spot with as
> small of a angle as possible.
> If one could, would there be problems with mismatched coherence or
> such of the mutiple beems?

I think you're getting at the beams being out of phase with each other and
forming nodes and anti-nodes? They will be at dead on the same wavelengths
of emission, the only tiny chance is that one may have traces of other gases
in there like nitrogen but you're not bothered about UV anyway. You get
nodes and anti-nodes set up really nicely with standing waves that are
reflecting back off something over themselves at precisely 180 degrees
difference. In this case you are super-imposing another beam of possibly a
different phase and so you should be able to set up nodes and anti-nodes.
CO2 has it's output line at 10.6um so that'd require some careful tweaking
with a rubber mallet.... :-) Like they did the first electron
microscropes. You could pump both tubes with the same power supply and then
try to mechanically align the lasers! I bet you'd be able to just dream away
the hours doing that. But just maybe, how about sitting one laser on a very
short length of linear rail and then using a micrometer to move the entire
setup until maximum beam power is observed? I think the system will probably
vibrate more than 10.6um just due to you walking around near it or the
machine moving.

> By the way. These Kits look like a cinch for hard core machinists.

They look like so much fun it's untrue. As for some of the guys on here,
they'd be a walk in the park for them to machine entirely themselves just by
looking at one. I would think it'd be much easier if you were to build a 55
watt laser and then if you want more, just build a bigger one in a single
tube. Lots of parts can be salvaged for these lasers, like the mirrors, gas
handling stuff, vacuum pump, coolant pump, power supply etc. About the only
part you'd couldn't carry on would be the tubing itself. One way to increase
power is to make the cavity inside wider and pump it with more power. What
you may want to do is buy specifically larger optics and then just remove
the old cavity, put in a wider one and widen out the mirror mounts a little.

I'm sure you'd be able to sell a CO2 laser for the same amount you bought it
for so long as it wasn't damaged or not well. There are some people out
there, even on this list, who just don't have the time to muck about making
a laser and will buy one off you to know it's going to drop in and work.

John H.