The thermal effect of laser rod is an important factor for the improvement of the output of solid laser. In this paper, the thermal compensation approach is employed. The thermal focal-length is measured and the curvature radius is calculated to determine the thermal compensation. The experimental technique raises notably the output of laser. There are several fluoresent bands in Nd~(3+):YAG. Some of the spectral lines in a band are close to each other. The cross-section of their transitions are also different. Thin solid etalom or combined solid efalons are used to tune the weak lines to lase.