Nd:Glass Multimode Laser Systems

The power of conventional solid-state laser systems is limited by the thermal load of the active material. One possible approach to solve this problem is to utilize a Nd-doped glass fiber as laser medium. We estimate power and efficiency of several fiber laser configurations arranged in a transverse pump-cavity. The calculations are based on single fibers using laser glass LG-760 (8 wt.-% Nd) as core material of the fiber pumped with available sources. One result is that the laser power is limited not necessarily by the length of the fiber but rather by gain saturation and by the damping loss of the fiber. Furthermore there is an optimum fiber length to maximize the efficiency which results in the fact that large efficiencies are correlated with small laser powers and vice versa. For the configurations under consideration, average powers up to 100 W seem to be attainable with an efficiency of 1 % in pulsed operation; on the other hand, maximum efficiencies at optimum fiber length are about 5% with powers of 5... 10W depending on the core diameter. For cw-operation maximum power and efficiency are reduced to about 40 W and 2.5 %, respectively, mainly due to the thermal population of the lower laser level at room temperature.