The growth of Yb:S-FAP [Yb<sup>3+</sup>:Sr<sub>5</sub>(PO<sub>4</sub>)<sub>3</sub>F] crystals is being developed for use as the gain medium in the Mercury Laser, a gas-cooled amplifier system intended to yield 100J, 10Hz and 10% efficiency in 3 nsec when completed, for inertial fusion energy. A number of defect issues have been overcome to produce high quality crystals, including: cloudiness, bubble core defects, anomalous absorption, low-angle grain boundaries, cracking, and crystal inclusions. Currently useful crystals are routinely produced for fabrication into full size slabs. However, stress cracking during fabrication is being addressed as a critical issue in producing the 14 slabs necessary for full activation of the Mercury Laser.

© 2003 Optical Society of America

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