大尺寸Nd^(3+):YAP晶体中云层和孪晶的克服途径

PREVENTION OF CLOUDINESS AND TWINNING IN LARGE-SIZE Nd^(3+): YAP CRYSTALS

本文报道用中频感应加热Czochralski法,在大的气-液温差场中生长大尺寸的Nd^(2+):YAP单晶,并在生长过程中采用“真空自然冷却法”退火工艺。即当大尺寸Nd^(3+):YAP单晶在高温下生成后,随即改变氮气氛成真空状态,由于真空状态下热辐射起主导作用,炉膛内温度梯度明显减少,使生成后的大单晶在这种由真空导致的低梯度的温场中自然冷却到室温。不仅可以克服云层的产生,而且可以克服孪晶的形成。

Large-size Nd^(2+): YAP single crystals grown by Czochraiski technique, i. e, heating induced by medium-frequency in the temperature field of large gas-liquid temperature difference, are reported in the paper. During the growth, the annealing technique of the Vacuum Natural Cooling Process(VNCP)is adopted. After the large Nd^(2+): YAP single crystals are grown at high temperature, the nitrogen atmosphere in the chamber immediately changes into the vacuum (10Pa)state. Thus, the temperature gradient reduces greatly in the chamber since the thermal radiation plays a major role in the vacuum state. The grown Nd^(2+): YAP crystal is then cooling naturally from high temperature to room temperature in such a temperature field. By means of the above technique, a batch of large-size Nd^(3+): YAP crystals free from cloudiness and twinning can be obtained.