Nd:YAG激光晶体开裂与缺陷研究

Study on the cracking and defects of Nd:YAG laser crystal

采用提拉法沿〈111〉方向生长Nd:YAG激光晶体时,经常会发生开裂现象。利用光学显微镜、扫描电镜(SEM)、X射线衍射仪和光吸收及化学腐蚀等仪器和手段,对开裂Nd:YAG晶体的缺陷特征进行研究。开裂Nd:YAG晶体中有很多不规则包裹物,包裹物内元素含量偏离正常成份;位错密度较高并有塞积现象,位错腐蚀坑中有微裂纹产生;分析表明Nd:YAG晶体开裂是由晶体生长后期的降温不均及生长速率的改变加剧了组分过冷带来的不良后果,产生包裹体造成局部应力集中所致。

Cracking in Nd： YAG laser crystals grown along （111） by Czochralski method is often observed. The growth defects in the cracked Nd：YAG crystal were investigated with optical microscopy, scanning electron microscope（SEM）, X-ray diffractometry and optical absorption method. There are a lot of inclusions in cracked crystal, whose composition deviates from the normal composition of crystal. The dislocation density is so high that the phenomenon of pile-up occurs. Some micro-cracks was observed in dislocations etch pit. Cracking results from stress concentration caused by inclusions, which is caused by components overcooling, fluctuating of growth rate and asymmetry of temperature gradient in later period of crystal growth.