So one of the other problems with high power lasers is cooling the lasing mechanism. A recent novel solution to that is to have a liquid with the same refractiv

So one of the other problems with high power lasers is cooling the lasing mechanism. A recent novel solution to that is to have a liquid with the same refractive index and to circulate it (with no turbulence) through passages within the lasing mechanism. That way it can be cooled very thoroughly without interfering with the light generation. (Probably the coolant doesn't contribute, but maybe it does.) Seems this can do on order of 5 kw/kw output.