Abstract

Crystals of Yb³⁺:Sr_5-xBa_x(PO₄)₃F (0 ≤ × ≤ 5) have been investigated as a means to obtain broader absorption bands than are currently available with Yb³⁺:S-FAP [Yb³⁺:Sr₅(PO₄)₃F], thereby improving diode-pumping efficiency for high peak power applications. Large diode-mays have a FWHM pump band of ≥5 nm while the FWHM of the 900 nm absorption band for Yb:S-FAP is 5.5 nm; therefore, a significant amount of pump power can be wasted due to the nonideal overlap. Spectroscopic analysis of Yb:Sr_5-xBa_x-FAP crystals indicates that adding barium to the lattice increases the pump band to 13-16 nm which more than compensates for the diode-array pump source without a detrimental reduction in absorption cross section. However, the emission cross section decreases by approximately half with relatively no effect on the emission lifetime. The small signal gain has also been measured and compared to the parent material Yb:S-FAP and emission cross sections have been determined by the method of reciprocity, the Füchtbauer-Ladenburg method, and small signal gain. Overall, Yb³⁺:Sr_5-x Ba_x(PO₄)₃F crystals appear to achieve the goal of nearly matching the favorable thermal and laser performance properties of Yb:S-FAP while having a broader absorption band to better accommodate diode pumping.

© 1997 Optical Society of America