Authors: Marc-André Lapointe, Stephane Chatigny, Michel Piché, Michael Cain-Skaff, Jean-Noël Maran
The thermal degradation of double clad optical fiber coatings is known to be the prime limiting factor for the operation of high power CW fiber lasers. In this paper, we conduct a study of thermal effects in high power CW fiber lasers. A particular focus is put on heating at the splice points and in the doped fiber due to the quantum defect in 100-W class CW fiber lasers. A theoretical model and experimental measurements taken with a high resolution IR camera on 125 to 400 μm diameter fibers are presented. Thermal contact resistance between the fiber and its heat sink are considered in the conduction heat transfer model and measured for different geometries. Proper designs for cooling apparatus are proposed and optimization of the active fiber is discussed. Some predictions for power scaling and temperature management of fiber lasers to kW power level are also described.