A MOPA with double-end pumped configuration using total internal reflection

We presented a Nd:YAG master oscillator power amplifier (MOPA) with the compact LD double-end pumped configuration. To acquire the homogenous absorption distribution, a composite short Nd:YAG rod has been employed as the amplification medium and the rod side was well polished to cause total internal reflection (TIR) at the internal wall of the rod. Because the axes of pump LDs and the seed laser occupy the same position, it is relatively easy to obtain both the satisfied mode-matching efficiency and the high absorption efficiency by using two stacked-LD modules. A seed laser, with the input energy of 15 mJ and the pulse width of 46 ns, was amplified through the MOPA structure with the one-pass gain of about 1.2. We have not found any parasitic oscillations from both ends of the amplifier rod until the total pump LD power reached 420 W. The proposed scheme is thought to be useful in a multiple-pass MOPA system for high-average-power applications.