Point-like Seed Grown Kdp Crystal Dislocations Research

KDP (KH₂PO₄) is a type of excellent electro-optical non-linear optical materials, which have been developed since the 20th century. KDP-type crystals are widely applied in the fields such as laser frequency change, electro-optical modulation and rapid optical switch. Because of its wide usage in these fields, a lot of KDP crystals with high quality are needed. This requires KDP crystals have large size, higher Laser Damage Threshold, lower absorption, higher homogeneity as well as fine transmittance.KDP crystals are usually grown by lowering temperature method in solution. Lowering temperature method can be classified into traditional slow growth and point-seed growth. In this dissertation, point-seed growth method was used to carry out crystal growth experiments. This method had manv advantages, such as rapid growth and high crystal utilization rate. It is usually unavoidable for several kinds of defect to appear in KDP crystals, such as growth stripes, dislocations and scatter. As a result, the crystals can't be practically used. So it is important to study the defects in KDP. Now that the formation of defects is complex, it appears quite fundamental for us to find out the formation mechanism, which is meaningful to improve the growth technology and improve the quality of KDP crystals.The dislocation on (100) crystal face of KDP crystal grown from the point-seed was observed and analyzed by the optical microscopy. The dislocation was not the same as that of the crystals grown by the traditional method. The dislocation mainly originated from the seed, which can be decreased by the following technology process in order: regeneration, dissolution and growth. When two dislocation lines with a very sharp angle met in the crystal. they would converge to line. After analyzing the KDP crystal growth with point seed, it was found that the expansion of (100) expended is related to the pH value in solution. The prismatic faces expand easier in the solution with high pH value. By comparing the spectral transmittance, the spectral transmittance of prismatic face is higher than the pyramid face.