1.047-MU-M YB-SR-5(PO4)(3)F ENERGY-STORAGE OPTICAL AMPLIFIER

The pumping and gain properties of Yb3+-doped Sr-5(PO4)(3)F (Yb:S-FAP) are reported, Using a tunable, free running 900-nm Cr:LiSAF oscillato r as a pump source for a Yb:S-FAP rod, the saturation fluence for pump ing was measured to be 2.2 J/cm(2) based on either the spatial, tempor al, or energy transmission properties of the Yb:S-FAP rod. The emissio n peak of Yb:S-FAP (1047.5 nm in air) is shown to overlap with that of Nd:YLiF4 (Nd:YLF) to within 0.1 nm, rendering Yb:S-FAP suitable as an effective power amplifier for Nd:YLF oscillators, The small signal ga in, under varying pumping conditions, was measured with a cw Nd:YLF pr obe laser. These measurements implied emission cross sections of 6.0 x 10(-20) and 1.5 x 10-(20) cm(2) for pi and sigma polarized light, res pectively, which fall within the error limits of the previously report ed values of 7.3 x 10(-20) and 1.4 x 10(-20) cm(2) for pi and sigma po larized light, obtained from purely spectroscopic techniques, The effe cts of radiation trapping on the emission lifetime have been quantifie d and have been shown to lead to emission lifetimes as long as 1.7 ms, for large optically dense crystals. This is substantially larger than the measured intrinsic lifetime of 1.10 ms, Yb:S-FAP crystal boules u p to 25 x 25 x 175 mm in size, which were grown for the above experime nts and were found to have acceptable loss. characteristics (<similar to 1%/cm) and adequately large laser damage thresholds at 1064 nm (-20 J/cm(2) at 3 ns), Overall, diode-pumped Yb:S-FAP amplifiers are antic ipated to offer a viable means of amplifying 1,047-mu m tight, and may be particularly well suited to applications sensitive to overall lase r efficiencies, such as inertial confinement fusion energy application s.