Quasi-phase Matched Crystals Fabrication And Relative Technology Research

The whole wavelength rang and the biggest non-linearity coefficient of the ferroelectric crystals can be utilized by the Quasi-Phase-Matched technology, so the nonlinear conversion efficiency of the Quasi-Phase-Matching is higher than the angle phase-matching. The Quasi-Phase-Matched technology can be achieved by changing the structure of the crystal factitiously for making the non-linearity coefficient of the crystal periodic. It is the development direction of the nonlinear optics.The Quasi-Phase-Matched technology has developed fast since the Electric field periodic poling method appeared. It is a new technique to create periodically inversed domain structures in ferroelectric crystals to fabricate Quasi-Phase-Matched device. Investigation on the theory and technique of domain inversing is the basis of fabrication of ferroelectric crystals with ideal inversed domain structures. The dissertation analyzed the principle of Quasi-Phase-Matched, the character of ferroelectric crystals, and the theory of domain inversing, designed and fabricated the high voltage power supply for the manufacture of Quasi-Phase-Matching device and the heating controller for the temperature-tuned. Major contributions are as follows:1,Based on Maxwell's equations, the couple mode equations between three light waves are educed and the formula of the efficiency of SHG is gained.2,Based on the character of ferroelectric crystals, investigated the theory and the technique of domain inversing and introduced the process of the fabrication of the Quasi-Phase-Matching device with Electric field periodic poling method.3,Analyzed the parameter of poling voltage which is for the fabrication of periodically poled lithium niobate (PPLN) and periodically poled KTP (PPKTP). Designed and fabricated two high voltage power supply for PPKTP. One can output trapezoid waveform and triangular waveform. Another can output square waveform whose rise time is short than 100μs. Many experiments were performed on KTP crystal by use of this power supply and the experimental results were gratifying.4,investigated the relationship between the error of the electrode period and the duty cycle and the SHG efficiency. Analyzed the temperature-tuned of the Quasi-Phase-Matched device. Designed and fabricated a heating controller for the temperature-tuned. Its control precision is±0.1℃and the highest working temperature is 220℃.5,Many poling experiments were performed on KTP and LN, and many SHG experiments were performed on the PPKTP and the PPLN which is fabricated by ourselves. The PPLN's normalization efficiency of SHG is 1.03%/W·cm and the PPKTP's is 1.69%/W·cm. The temperature-tuned experiments were also performed and the experimental results were analysed.