The Czochralski Growth Of Laser Crystal Nd:YVO₄ By A Novel Method

With the improvement of laser technology in recent years, laser crystals are needed greatly in every aspects of our daily life, such as aeronautics technology, satellite positioning, exploration and measurement, medical equipment and special lighting. Nd:YVO₄ is one of the most important crystals in science research and industrial production due to its superior laser properties and is proved to be more and more prominent in laser display technology. The improvement of Nd:YVO₄ crystal promotes the fabrication and industrialization of laser display devices greatly, leading a much more colorful life in future.However, the Czochralski growth of Nd:YVO₄ crystal is rather difficult. After unremitting efforts of many researchers for a long time, the Czochralski growth parameters of Nd:YVO₄ has been established basically and the technological process is relatively mature. In spite of this, the process still calls for improvement imperiously because large size and high quality Nd:YVO₄ crystal is lacked badly. The thesis aims at the growth of high quality Nd:YVO₄ crystal and a new craft is studied from the viewpoints of the theory and experiment. An intact new growth circuit is designed and attempted for good Nd:YVO₄ crystal.The thesis is divided into three sections as following.1. The development of laser crystals and Nd:YVO₄ crystal is reviewed briefly.2. An abnormal crucible designed by ourselves has been used in new growth technology and the varieties of related physical quantities has been calculated via math modeling and physical simulation, such as natural convection, forced convection, growth interface, temperature distribution, temperature gradient, crystal defects, rotation rate, crystal diameter etc. Meanwhile, the quantitative relationship of some parameters is obtained.3. The effect of abnormal crucible is studied based on theory calculation and conventional process and the whole Czochralski technique is offered entirely and improved, in order to guide industrial production. Specifically, the selection of devices, the preparation of raw materials, the production of crucible, the structure of furnace, the manufacture of seed crystals and every parameters of Czochralski method (crystal washing, seed crystal, necking, shoulder, diameter, annealing, etc.) are discussed point by point. Some tests of as-prepared Nd:YVO₄ crystal are made in comparison with conventional crafts. Finally, an optimized technique is given for evaluation in future research.In summary, this thesis has studied the growth of high quality Nd:YVO₄ crystal by a new craft both in theory and experiment, which is viable in industrial production. It is the first time of design and usage of'Abnormal Crucible'in Czochralski growth of Nd:YVO₄ crystal. This improvement is very helpful for the crystal quality without additional difficult of operation compared to the original process. It is obvious that the work provides an useful direction of the development of Nd:YVO₄ crystal growth with large scale and high quality.