Of Fe ~ (3 +) Ions Influence The Performance Of Kdp Crystal

Phosphate such as KDP (KH₂PO₄) crystals are non-lineal optical crystal materials with good optical qualities . They have high nonlinear optical coefficient, broad transparent optical band, well optical uniformity, large scale in size, and easy to realize phase matching. So it has been widely used as laser frequency conversion, electrooptical modulation and optic switch in the high technology fields. With the development of program of inertial confined fusion (ICF), larger scale in size and higher optical qualities of KDP crystals is needed.It was traditionally thought that impurity ions have negative influence on the optical qualities and damage thresholds of KDP crystals. Irons are adulterated in the raw materials and can't be eliminate entirely. Having the characteristic of absorbing ultraviolet, holding back the extension of the prismatic, even bring wedge phenomenon, it is an important ions needed to be paid attention. In this paper, the transmission and Laser Damage Threshold (LDT) of the KDP crystals with different concentration of Fe³⁺ dopant are tested and analyzed. So the influence of trivalent (Me³⁺) and bivalent (Me²⁺) cations in potassium dihydrogen phosphate (KDP) crystals can be deduced.The crystals with different concentration of Fe³⁺ dopant grown with traditional and rapid method are cut perpendicular to the crystal's Z axis, and surface of the z-plate is polished. Testing on the z-plate we find that the transmission of sample grown with traditional method is decreased with the increase of the concentration of Fe³⁺ dopant, and the decrease is more clearly with the more concentration of Fe³⁺ dopant. And it change slightly in different region of the sample. Testing on the sample grown with rapid technology, we find that the transmission of samples is decreased with the increase of the concentration of Fe³⁺ dopant too, but the transmission of different region as in the center (pyramidal sector) and in the edge (prismatic sector) is different clearly. The transmission of violet in the center is much higher than the transmission of violet in the edge. The concentration of Fe³⁺ dopant is different in crystals grown with different methods as traditional method and fast technology, and the concentration of Fe³⁺ dopant is different in different region as in the center (pyramidal sector) and in the edge (prismatic sector). Fe³⁺ ions have clearly absorption of ultraviolet.Testing on the KDP crystals we found that the laser damage threshold of the samples decrease clearly with the concentration of Fe³⁺ dopant increasing both on the crystals grown with traditional method and with rapid technology. Light scatting techniques and Phase Contrast was used to observe defect and damage in the bulk of KDP crystals during the damage testing. With the two methods we make sure that the damage occurs in certain situation. And we made a comparation of the two methods too. With Light scatting techniques we can observe defect and damage timely and sensitively. And with Phase Contrast we can get the shape of damage clearly. Two means combined to observe the damage can help to realize the mechanism of damage in the crystals. We observed the sprinkle like fog and grain in the front and back surface of the crystals during the illumination of the laser on the crystals, and we made an analysis on the phenomenon combined with the theory of laser conditioning and laser damage on the crystals.Measuring the interference pattern of light for the crystals, we found that the concentration of Fe³⁺dopant haven't clearly influence on the stress and refraction within the crystals.S. G. Demos in the Lawrence Livermore National Laboratory use microscopic fluorescence imaging to detect optically active centers located inside the KDP crystals. Because of the distribution of Fe³⁺ions in the crystals and the absorption of ultraviolet, we plan to observe the crystals with different concentration of Fe³⁺dopant using microscopic fluorescence imaging, and study the characteristic of Fe³⁺ions in the crystals.According to the research of the characteristic of Fe³⁺ions in the KDP crystals we can speculate the characteristic of high valence metallic ion in the KDP crystals, and we believe that high valence metallic ion such as Fe³⁺ions is very important reasons to the damage of KDP crystals.