Fiber attachment for 980 nm pump lasers

Analysis showed that a new clip design is needed meeting the following requirements: (a) suitability for automation (e.g. handling, laser welding and fine adjustment), (b) tolerance for gaps between the rod and the clip walls to obtain good weld spot quality, (c) stable pivot point for readjustment by applying plastic deformation and (d) flexibility for assuring bending of the clip rather than in the rod. These requirements have been addressed by the clip design presented in this paper. The clip is made of Kovar using high precision electro-erosion techniques. It consists of a rigid front section and a flexible back section. The fiber is fixed by laser welding to both sections. The weld in the rigid front section acts as pivot point whereas movements on the back part results in fiber tip travel with an approx. 5:1 ratio. The final mechanical fine adjustment is done by bending (plastic deformation) the flexible back part of the clip or by laser hammering. This flexibility assures that the clip bends rather than the rod itself, which could lead to reliability problems. The flexibility was achieved by narrowing and rounding off the joints between welding area and clip base as well as by the positioning of the laser welds