Fig. 1. Laser configuration (patent pending) is shown. Each pump beam (①,②, ③, and ④) is directed from the corresponding optical fiber (F) to the composite Nd:YAG/Cr4+:YAG medium through a lens (L) and a folding prism (P). Four (1, 2, 3, and 4) laser beams are obtained.

Fig. 2. (a) Laser pulse energy Ep versus distance d2 between lens L and surface S1 of Nd:YAG. Data for two lenses, first with focal length f=4.0  mm placed at distances d1=3.4 and 4.4 mm from F, and the second with f=6.2  mm positioned at d1=4.9 and 5.9 mm from F, are shown. The inset is a sketch of the single pump-beam arrangement. (b) The corresponding pump pulse energy, Epump, is plotted.

Fig. 3. Laser pulse energy Ep versus laser beam radius ωg. Losses Li=0.01, and, for Cr4+:YAG, final transmission Tf of 0.94 and 0.98 were considered in simulations.

Fig. 4. (a) The module with the four folding prisms is presented. Each lens (L) position is indicated. P: prism. (b) A photo of the Nd:YAG/Cr4+:YAG laser with four-beam output is shown. The directions of laser beams 1, 2, 3, and 4 are given by the colored lines with arrows.

Fig. 5. Maximum temperature of surface S2 of Nd:YAG/Cr4+:YAG at central locations of beams 1 and 4 versus the pump pulse repetition rate.

Fig. 6. Several combinations for focusing the laser beams are shown: (a) focusing in a single point; (b) focusing all beams in the same plane, at equal distances from the optics; (c) beams 1 and 3 (from the horizontal plane) are focused before beams 2 and 4 (from the vertical plane); (d) beams 2 and 4 are focussed close to the optics, in front of beams 1 and 3.