Cr4+:YAG passive Q-switching of directly pumped Nd lasers

The optical pumping into the 4F3/2 emitting level of Nd lasers has received special attention in the last years as a means for increasing the laser performances and reduction of heat generation. These advantages were first demonstrated for diluted [1] or concentrated [2] Nd-doped YAG or YVO4 under pumping with Ti:sapphire laser in the region of 0.88 µm. By a careful design of the laser configuration, continuous-wave laser emission at 1.06 µm with nearly quantum defect limited slope efficiencies of 0.80 in Nd-vanadate crystals [3] and of 0.79 in Nd:YAG [4] was soon reported. This paper investigates the possibility to improve the passively Q-switched emission of Nd lasers by direct pumping at 0.88 µm with diode lasers. Average output powers in excess of 1.0 W are reported by switching with Cr4+:YAG saturable absorber (SA) crystals. The influence of doping level on laser characteristics is discussed. Results obtained under the pump at 0.81 µm, into the highly-absorbing 4F5/2 level, are given for comparison.