1.047-/spl mu/m Yb:Sr/sub 5/(PO/sub 4/)/sub 3/F energy storage optical amplifier

The pumping and gain properties of Yb/sup 3+/-doped Sr/sub 5/(PO/sub 4/)/sub 3/F (Yb:S-FAP) are reported. Using a tunable, free running 900-nm Cr:LiSAF oscillator as a pump source for a Yb:S-FAP rod, the saturation fluence for pumping was measured to be 2.2 J/cm/sup 2/ based on either the spatial, temporal, or energy transmission properties of the Yb:S-FAP rod. The emission peak of Yb:S-FAP (1047.5 nm in air) is shown to overlap with that of Nd:YLiF/sub 4/ (Nd:YLF) to within 0.1 nm, rendering Yb:S-FAP suitable as an effective power amplifier for Nd:YLF oscillators. The small signal gain, under varying pumping conditions, was measured with a cw Nd:YLF probe laser. These measurements implied emission cross sections of 6.0/spl times/10/sup -20/ and 1.5/spl times/10/sup -20/ cm/sup 2/ for /spl pi/ and /spl sigma/ polarized light. Respectively, which fall within the error limits of the previously reported values of 7.3/spl times/10/sup -20/ and 1.4/spl times/10/sup -20/ cm/sup 2/ for /spl pi/ and /spl sigma/ polarized light, obtained from purely spectroscopic techniques. The effects of radiation trapping on the emission lifetime have been quantified 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 up to 25/spl times/25/spl times/175 mm in size, which were grown for the above experiments and were found to have acceptable loss characteristics (>