GROWTH AND CHARACTERIZATION OF HIGH-QUALITY ND3+-YAP LASER CRYSTALS

During the growth of large Nd3+: YAP crystals by the Czochralski method, the temperature gradient requirements to eliminate cloudiness and twinning in the crystals are completely different. A larger gradient is required during growth, whereas a smaller gradient is needed after growth (during an annealing step done in the same chamber). By changing the atmosphere from N2 during growth to a vacuum during annealing, a larger gradient could be created during the growth stage and a smaller gradient for the annealing process. With the above technique, the annealing period was greatly shortened and a batch of high-quality Nd3+: YAP crystals free from cloudiness and twinning was obtained. Rods with a diameter of 8 x 150 mm could be cut from the above crystals and a maximum average power of up to 781 W laser output has been achieved by using only a unitary rod.