Study On Fabrication Of Periodically Poled LiNbO₃ And Application Research Of Quasi-phase-matched Technology

This work is supported by both scientific research key project fund of Ministry ofEducation and national Nature Science Foundation. In this dissertation,quasi-phase-matched technology's basic theory and its application are deeplyresearched by theoretical ways. Many formula is worked out which is in agreementwith the experimental data. And further more, this dissertation analyze and describethe character of LiNbO3 crystal and its periodically poled experiment in detail.Quasi-phase-matching (QPM) is a technique for phase matching nonlinear opticalinteractions which the nonlinear coefficient is modulated spatially at regular intervalsusing a structural periodically built into the nonlinear medium. Using this technique,higher conversion efficiency can be obtained and nonlinear interactions over the entiretransmission band of the material can be utilized. In particular, the periodically poleddomain structure in LiNbO₃ has become the most important sample, which wasfabricated by domain engineering.LiNbO₃ (LN) crystal is one of the perfect materials to achieve the QPMtechnology. LN now develops rapidly because of its character of higher effectivenonlinear coefficient. In recent years, LN crystal pulling and PPLN fabricationtechnology has made much progress. So its application in nonlinear frequencyconversion becomes more and more wide. Dissertation deeply researches the basictheory of QPM as well as the method to achieve QPM technology. Majorcontributions are as follows:1,Based on Maxwell equations and theory of nonlinear polarization, the couplemode equations are educed which is used to describe the interaction between threelight waves in dielectric. And on the basis of this conclusion, the frequencyconversion efficiency of SHG is analyzed in detail.2,Based on effect nonlinear coefficient's Fourier transform, the couple modeequations are educed and solved under the QPM condition. From these conclusions,we analyze the restricted relationship between the frequency conversion efficiency ofSHG and the parameter of periodically poled crystal.3,Dissertation analyze the physical, chemical and ferroelectric character of LNcrystal. When use method of external electric field poling, the ferroelectric domaininverted course is described. And then the character of dielectric breakdown isanalyzed from theory and validated from experiment.4,The high voltage and microsecond pulse power is presented which is used inperiodically poled experiment of LN crystal. Then we describe the fabricated courseof PPLN and two methods of external electric field poling. And at the same time aseries of experimental result is presented. Finally, we experiment on the SHG ofPPLN crystal and obtain the result for our future work.5,Dissertation analyze the all-optical wavelength conversion(AOWC) technologybased on PPLN waveguide in detail. The couple mode equations are educed which isused to describe the cascaded second-order nonlinearity based on sum-frequencygeneration (SHG) and difference-frequency generation (DFG) in nonlinear waveguide.And on the basis of these conclusions, the frequency conversion efficiency of SHG isanalyzed in detail. The differences between couple mode equations in nonlinearcrystal waveguide and in generic medium disappear due to a series of united operation.So the uniform equations offer basic theory for our future work.