High-Quality, 4 x 6 cm 2 , Yb:S-FAP [Yb 3+ :Sr 5 (PO 4 ) 3 F] Crystal Slabs for the Mercury Laser

The growth of Yb:S-FAP [Yb3+:Sr5(PO4)3F] 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.