【作者】 纪磊；

【导师】 武星；

【作者基本信息】 天津大学 ， 物理电子学， 2005， 博士

【摘要】 铌酸锂晶体拥有一系列独特的电光、声光、弹光、压电、热电和非线性光学特性,这使得它成为声光、电光和非线性光学器件等应用中最具吸引力的材料之一。基于准相位匹配技术的周期极化铌酸锂(PPLN)可以利用铌酸锂最大的非线性系数d33(25.2pm/V),已广泛应用于倍频/差频、光参量振荡等光参量过程和THz波产生等方面。在光通信领域,尤其是波长变换、全光开关方面,也有广阔的应用前景。本文侧重于研究铌酸锂畴反转基理,并基本解决极化工艺的实际问题,完善极化工艺,为进一步提高周期极化铌酸锂器件的性能奠定基础。论文采取理论分析与实验验证紧密结合的研究方法,所涉及的研究成果与创新之处如下:1.利用有限元法分析了周期极化电极结构的电场分布。比较了梳形电极与框形电极的优劣。在理论分析的基础上提出一种适用于小尺寸晶片的能有效降低边缘电场的周期极化电极结构,并申请了发明专利(申请号: 200510015505.6)。2.系统分析了各种可能的工艺缺陷对极化质量的影响。其中包括液体电极方案可能存在的气泡问题,提出了相应的对策;多种周期同时极化时,各部分在极化进程中相互之间的影响;以及毛刺、断条光刻缺陷对极化质量的影响。3.利用斯坦福大学提出的数学模型对绝缘层介电常数、绝缘层厚度、电极宽度、外加电压幅度和光栅周期对极化进程的影响进行了分析,提出选择各参数取值的原则,并给出由光栅周期计算最优电极宽度的拟合公式。4.纠正了一篇重要文献中不正确的合成频谱调谐曲线,并分析了导致问题产生的算法错误。5.提出了更符合铌酸锂周期极化过程实验结果的三维动态模型。6.研究了与铌酸锂周期极化密切相关的击穿特性。7.设计了液体电极方案的极化夹具,改进了已有的极化电源。8.制备了有效通光长度20mm的周期极化铌酸锂样品,对连续光Nd:YVO4激光器1064nm波长一阶准相位匹配倍频过程进行了实验研究,在1.51W的基频泵浦功率时得20.55mW 532nm的倍频绿光输出,其倍频转换效率为1.36%,较我们之前的效率提高了26倍。达到国内相同实验条件下类似研究的一般水平。9.对近化学计量比铌酸锂和抗光折变掺杂铌酸锂的极化和击穿特性进行了初步研究。更多还原

【Abstract】 Lithium niobate crystal has a serious of outstanding properties of electro-optics, acoustic-optics, plastic-optics, pizoelectronics,pyroelectricity and nonlinear optics, which make it one of the most attractive materials for acoustic-optical, electro-optical and nonlinear optical devices. Periodic poled lithium biobate (PPLN) based on quasi-phase matching (QPM) technique uses the largest nonlinear coefficient of lithium niobate d33(25.2pm/V), and is widely used in parametric process, such as second harmonic generation, differential frequency generation, optical parametric oscillation, in THz wave generation, and is an promising technique in the field of optical communication, especially in wavelength conversion and all-optical switching.We emphasized our study on the basis of domain reversion of PPLN, roughly solving substantial problems of poling process, optimizing poling process, and building an well-developed platform readily for further improvements of the quality of PPLN device. The work integrated theoretical analysis and experimental evidence, and its major contribution is listed as follows:1. The electric field distribution of poling structure is analyzed with finite element method. A comparison is made between comb-like and frame-like electrode structure. A novel periodic poling electrode structure which efficiently decreases the fringe field and is suitable for the poling of crystal with a small dimension is proposed based on theoretical analysis. This structure is applied for an invention patent. (application no.: 200510015505.6).2. The influence of several potential defects on the poling process is systematically analyzed, which includes the residual bubble issue of liquid electrode method with an countermeasure proposed; the interaction of different parts when multiple period is simultaneously poled; the influence of small protrusion and broken strip on poling process.3. Five important geometric parameters in periodic poled lithium niobate, permittivity of insulator, thickness of insulator, width of electrode, applied voltage and period, are numerically analyzed with a computational model from Stanford university. A general procedure in the design of poling configuration is thus obtained. The square regression formula for the relationship of width of electrode versus period achieved here will be an useful assistant of the design process.4. Corrects the synthesized tuning curve from an important reference, and points out the major algorithm mistake.5. An 3-D kinetic model which demonstrates the poling process precisely is presented.6. Study the break-down characteristics of lithium niobate which is intrinsicly related to the poling process.7. A practical jig used for liquid electrode method is designed, and the high voltage supplier is revised for higher performance.8. A 20mm-long PPLN is fabricated and characterized for the first order second harmonic generation of 1064nm continuous wave Nd:YVO4 laser. A 20.55mW green light of second harmonic is obtained when the pump power is 1.51W. The corresponding conversion efficiency is 1.36%, which improves 26 times than our early results, and reaches the average of domestic research under the same condition.更多还原