Argon lasers are hideously inefficient due to the quantum mechanical nature of the argon atoms you can expect an efficiency of about 0.01%.
from a regular 120 volt socket you can get at the most 120V x 15A = 1800 Watts.
0.01% of that is 180mW. If you factor in the losses in the heated cathode, fans, passbank and other circuitry, you would be lucky to get 80mW out of one of these.
Those small cylindrical argon tubes typically are rated at 20-40mW and you will probably get closer to 15-20mW except when its new i would expect. If you swap out the optics for multiline optics, assuming the optics are external, you might be able to get 5mW more then before in total but aligning optics is no walk in the park without an optical bench and some experience. But that AO modulator is a great find, if it works it's easily worth what you paid for the whole package.
Just for god sakes don't run that thing without the blower on it.
The sticker on mine says 400mW maximum but i never get more then 45mW out at maximum power. They make it higher then it really is because when it's brand new the optical gain is huge and you get a ton more power then you are supposed to.