The fused silica light guides of cross sections (5X5mm) were provided by Beijing King Quartz Cooperation. The light guides are of good optical quality. Four light guides were curved to a designed curvature under high temperature environment (hydrogen flames). A pure graphite mould was also used to help the correct bending of these light guides. The other four light guides in diagonal positions were firstly curved to the desired shape. The input ends were then twisted 900. It was discovered that a much better light concentration to the crystal was achieved by twisting the light guides at their input ends. In order to fit compactly these light guides into free spaces in diagonal positions in Fig.5, the input end of the twisted light guides should be carefully polished. For focusing tightly the solar power to the central core region of the laser crystal, the input ends of all these light guides were slightly and spherically polished. The output ends were also polished in cylindrical lens shape.

Fig.7 The output ends of five principal Fig.8. End and side pumping scheme

light guides for end-side pumping. light guide assembly.

The four light guides in diagonal positions were removed to demonstrate clearly the free space where the flow tube is to be mounted. The output end of the central light guide was used to realize end pumping and the others were used for side pumping.

The side-pumping scheme from eight light guides is shown in Fig.8, where the central focus region was clearly seen. Light guides from eight directions could pump the laser crystal uniformly.