The power of the laser is dependent of several things. First thing is the current and the gas mixture. The higher the current, the higher the power (up to the saturation point). You can check it out yourself : why do you need just these three gasses (CO2, N and He)to make the CO2 laser work. The energy of the discharge is first absorbed by the Nitrogen (that's also the "pink" discharge color which you see in the tube), the Nitrogen transfers the energy to the CO2 molecule and the heat that arises is carried to the "wall" by the Helium. Second thing, where the voltage comes in, is the length of the discharge. The longer the discharge length, the more power, but also the more power you need to start the discharge (ignition). Further is the gas flow also of importance. The more "fresh" gas is present and "old" gas renewed, the more power (if possible you could consider building a fast flow CO2 laser). Also other factors like the gain, inversion population, resonator design, cooling and the output coupler mirror have to be taken in account when you want your laser to give the most power.

    Gas mix has a tremendous effect on power. That looks like too much CO2. You would probably get more power with 7% CO2 and 18% N2, but you generally have to establish the optimum CO2: N2 ratio by tweaking anyway. If usually start at low CO2 and increase it the power goes up until a saturation point. Beyond that, the excess CO2 absorbs photons and the power drops. Increasing nitrogen increases the voltage. You get more power with more voltage until the discharge breaks down.

    CO2 lasers operate at reduced pressures with a CO2, N2, and He gas mixture. It's been a while but seems to recall that 1:2:3 CO2:N2:He worked OK at roughly 1/2 an atmosphere . They can also work at higher pressures but tube limitations (strength and window mounting) play a role - 4 Watts is plenty of power to damage eyes, etc. Caution is advised!

    DC discharge CO2 lasers run 30 to 80 torr (1 torr = 1/760 of an atmosphere, one atm is 14.7 psig). RF driven CO2 lasers can run from 30 torr to over 120 Torr for waveguide operation.

    If you add CO you push the equilibrium to the left, less CO2 >dissociates, you keep more of the active laser gas in its correct form, so to speak. It happens that the CO vibrational level is close to the N2/CO2 sym. stretch level, & can fullfill a similar role to N2 in the >mix (not quite as well.) Oxygen on the other hand tends to lead to discharge instability & more problems with electrodes.

    So many CO2 lasers work better with a little CO in the mix; just how much depends on the details of the laser. It wd *probably* work without any CO; up the CO2 & the N2 a bit to compensate; but you wd loose some power, & might have discharge stability problems.

    CO of course is very toxic, & cummulative over many hours, so some people dont like using it.

    In the discharge there are a lot of other processes. There are also other componets: molecules N2O, O2, CN etc, ions O3(-), O(-), CO3(-) etc., excited molecules and atoms. To calculate all processes is not possible in theory. The chemical composition is defined by experimental investigation only.

    Whilst these other processes certainly *exist*, they are of very minor importance compared to the basic CO2 chemical equilibrium, and have relatively little effect on the laser. It happens that in the past I made extensive measurements of nitrogen oxides etc in big CO2 lasers; their main effect related to discharge stability & electrode corrosion processes, they are too low level to have much effect on the laser kinetics.

    The situation in CO lasers is very different to that in CO2; a low gain laser, notoriously touchy on gas purity etc, with a quite different pumping mechanism (anharmonic collisional up-pumping & direct e impact as opposed to v-v resonant transfer).

    Incidentally, just to further complicate things, a very few CO2 lasers actually add O2 to the mix; again it suppresses the dissociation of CO2 & production of CO. For completeness, Xe is often added to small sealed CO2 lasers (not big, costs too much.) Basically it tailors the electron energy distribution in the discharge & improves the pumping efficiency.