High-repetition-rate low-energy-pulse pumping of Nd-YAG lasers

Several recent studies have compared xenon and krypton discharges as optical pumps for CW Nd:YAG lasers. Above 50 joules, xenon is reportedly more efficient, and in the 15-50 joule range, krypton has been found to be more efficient. We have compared the laser efficiencies obtained using pulsed discharges in xenon and krypton at pressures up to 3000 Torr and repetition rates up to 350 pps. Input energy was varied over the 0.5 to 10 joule range at pulse widths of 20, 100, 240, and 500 microseconds. Effects of pump-bore diameters of 1.7, 2.3, and 5 mm and bore lengths of 30 and 50 mm were evaluated using a quartz envelope--moly ribbon foil seal tube design and a keep-alive mode of operation. A 6-inch-diameter gold-coated sphere was used as the cavity for laser rods of 3, 5, and 6.25 mm diameter. Efficiency was found to increase with gas pressure up to 3000 Torr. A maximum efficiency of 1.8% was obtained with krypton, which, depending on current density, was generally found to be 20% better than xenon.