lasersafe1 wrote:...The DC tube is "randomly" polarized and "always" changing. Even if you place a linear polarizer in front of the tube and throw away 1/2 your light to make linear light for the AOM, it's randomness might make the linear output power swing around wildly. I'm wishing you luck, but I don't think it will work....
I'm an unabashed optimist usually, but i've learned the hard way not to pick a fight with the laws of physics. I have to agree with lasersafe1 here. But this could work if you used a laser tube without the built-in cavity optics, with say brewsters windows, or maybe just the one total reflector at one end. Then you could insert the AO cell in the cavity before the output mirror so it works as a Q-switch. I've seen a few such laser tubes advertised on Chinese manufacturer's websites. in theory they should cost less.
lately I have been doing a lot of late night reading on laser physics...
From what ive read, the root of the problem of quickly switching on & off the laser output, is the limit imposed by the excited state species lifetime in these lasers, which it seems are in the 1-100mS range, depending on a few factors, mainly gas pressure. If you're moving the beam on the workpiece at 1m/S the laser will keep lasing several mS thus several mm past the point where you cut the power to the tube.
The point is that this is a result of the physics in the laser tube design, much more than the CO2 gain medium.
With all my recent reading on this, I am pleasantly surprised to see how much laser technology, especially CO2, has progressed in the last couple of decades since the last time i was enamored with lasers.
Other types of CO2 lasers exist that have huge advantages over these sealed gas tube types which include, among other things, a much much shorter excited state lifetime and therefore the ability to be power-modulated at much quicker rates, by several orders of magnitude. No exotic optics, AO cell / Q-switch necessary.
If i didn't already have a ridiculous number of unfinished projects and new ones in the pipeline after them, id be very tempted to try to build one of the "modern" types of CO2 lasers.
One of the last papers i read describe a RF-excited TEA waveguide design that's made with only a few slabs of aluminum bar, no glass at all, and can easily get a couple hundred watts out of a 18" long cavity, and running at higher pressure means more than fast enough output response. And easier gas fill. Plus water-cooled electrodes means the the gas is conduction cooled right in the cavity so with no forced gas circulation it might be possible to run it sealed or semi-sealed at 100W or more. Seems eminently hackable. Hmmm.... anyone here own a CNC mill that can machine an 18" Al. bar in 1 pass?