is in higher efficiency than yag and co2 laser cutting machine. As fiber lasers are quasi-three-level systems. A pump photon excites a transition from a ground state to an upper level; the laser transition is a drop from the lowest part of the upper level down into some of the split ground states. This is very efficient: For example, ytterbium with a pump photon at 940 nm produces an emitted photon at 1030 nm-a quantum defect (lost energy) of only about 9% (see table).

In contrast, neodymium pumped on its standard 808 nm pump line has a quantum defect of about 24%. So ytterbium has an inherently higher efficiency, although not all that efficiency can be realized because some photons are lost. Ytterbium can be pumped in a number of bands. Erbium can be pumped at either 1480 or 980 nm; the latter is not as efficient from a photon defect point of view, but is useful even so because better pump sources are available at 980 nm.

Overall fiber-laser efficiency is the result of a two-stage process. First is the efficiency of the pump diode. Semiconductor lasers are very efficient, with on the order of 50% electrical-to-optical efficiency. Laboratory results are even better, with 70% or even more of the electrical pump energy being converted into light. When this output is matched carefully to the fiber laser's absorption line, the result is the pump efficiency.

The second is the optical-to-optical conversion efficiency. With a small photon defect, high excitation and extraction efficiency can be achieved, producing an optical-to-optical conversion efficiency on the order of 60% to 70%. The result is a wall-plug efficiency in the 25% to 35% range.