【作者】 贾宝申；

【导师】 赵业权；

【作者基本信息】 哈尔滨工业大学 ， 飞行器设计， 2011， 博士

【摘要】 光参量振荡器(OPO)是产生可调谐激光的一种非常重要的手段,它能够将一束泵浦激光转换为相干输出的信号光和闲频光,且可以在较宽的频率范围内实现可调谐输出。OPO实现的在军事上具有很高应用价值的3~5μm范围可调谐激光,在激光雷达、光电对抗、遥感、数据通信、光电测量等领域已显示出重要的应用价值。结合准相位匹配技术实现光学参量转换,是实现3~5μm可调谐激光输出的有效手段之一。过去人们制备基于准相位匹配技术的光学器件主要集中在同成份钽酸锂、同成份铌酸锂和磷酸氧钛钾等材料上。相对于以上材料,化学计量比钽酸锂(SLT)拥有一系列独特的非线性光学性质,尤其是较低的矫顽场和较高的抗光损伤能力,使得它成为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化学计量比钽酸锂(PPSLT)可应用于光参量过程并可产生3~5μm范围可调谐激光,显示出广阔的应用前景。基于这一背景,本文着重于SLT晶体的生长及PPSLT的制备技术和理论研究,涉及的主要内容有:采用添加助熔剂方法生长SLT晶体。研究大尺寸、组分均匀的SLT晶体的原料配比、生长以及后续处理技术。通过优化温场的温度分布和控制合适的生长工艺参数,从中频加热炉中生长出无明显宏观缺陷、光学均匀性好的非掺杂和掺镁化学计量比钽酸锂单晶。通过居里温度、紫外吸收边等测试手段研究了晶体的性能,证实了晶体的组分达到近化学计量比,其中通过居里温度测定晶体中的Li含量达到了49.8%[Li/(Li+Ta)]。测定了晶体的矫顽场及晶片平面内的矫顽场分布,非掺杂晶体的矫顽场只有2400V/mm且在晶片平面内变化很小。测试结果表明SLT是制备准相位匹配器件的理想材料。深入研究了SLT晶体的铁电畴极化反转的动力学机理,确定出影响铁电体反转质量的各种因素。从钽酸锂晶体的微观结构出发,详细讨论了晶体畴反转各个阶段的机理,研究了铁电畴反转动力学的基本规律。在大量极化实验的基础上,建立了铁电畴反转过程中各参数,如极化时间和极化电压等之间的函数关系。从理论上探讨了准相位匹配技术,并结合SLT晶体的实际,设计了产生3~5μm波长激光的超晶格结构和相应的调谐方式。利用自行制备的SLT晶体和周期极化设备进行周期极化实验。尝试了金属薄膜电极、复合电极和液体电极的极化方法,并根据SLT晶体铁电畴反转动力学的研究结果和周期极化实验结果,确定最佳的电极结构与极化工艺,成功制备了周期30μm的单周期PPSLT和3个通道的多周期PPSLT。设计了基于极化电流反馈的周期极化自动控制系统,并进行了周期极化的自动化控制实验。分析了可调谐中红外光参量振荡器相关的基础理论,如光参量振荡器和产生器中的三波互作用理论以及光参量振荡器的基本理论等。分析了如何设计基于PPSLT晶体光参量振荡器的关键环节。利用高重复频率全固态Nd:YAG激光器端面泵浦单周期PPSLT晶体,实现了中红外准相位匹配光学参量振荡。利用温度控制器的温度调谐,获得3.34~3.64μm波段的波长调谐输出。当平均泵浦功率为7.5W,温度为160℃时,得到了平均功率大于800 mW的中红外激光输出。更多还原

【Abstract】 Optical parametric oscillator （OPO） is one of the most important ways to get tunable lasers. The pump light could be converted into signal light and idler light by this way. Meanwhile,it can generate tunable coherent light. The broadband tunable laser generated by OPO have shown great value in data communications, optoelectronic measurements, laser range finder, laser radar, photoelectric confrontation and other fields, particularly the mid-infared laser with 3⁵μm-wavelength has great value in military. It is one of the most effective ways to get 3⁵μm tunable laser through optical parametric conversion by using quasi-phase-matched （QPM） techneque. In the past, congruent LiTaO3, congruent LiNbO₃ and KTiOPO₄ were used to make QPM devices. Compeared with these materials, stoichiometric LiTaO₃（SLT） has a serious of outstanding properties of nonlinear optics, especially the lower corecive field and higher anti-photorefractive ability, which make it one of the most attractive materials for making nonlinear optical devices. Periodic poled stoichiometric LiTaO₃ （PPSLT） based on QPM technique is widely used in parametric process. 3⁵μm tunable laser also could be generated through PPSLT. Based on this backgroud, this dissertation focus on the growth techneque of stoichiometric LiTaO3 and fabrication techneque of mid-infrared OPO based on SLT. In this thesis, the main contents are following:Stoichiometric lithium tantalate crystals were grown by flux method. To obtain SLT crystal with large size and uniform component, mixture ratio of raw material is studied and optimum value is gained. Processing method of subsequent crystal is also presented. By optimizing temperature distribution and selecting appropriate growth technical parameters, crystals with good optical homogeneity and no macroscopic defects have been grown. The composition of the grown crystal was assessed by measuring the UV absorption edge, Curie temperature and so on. The assessed Li content in the grown crystal is 49.8% by testing Curie temperature. The coercive field of the grown crystal is 2400V/mm. The distribution of coercive field in a wafer was tested and the result indicates that SLT is a good candidate for QPM devices.The domain reversion kinetics of SLT was studied and the factors that influence domain reversion were determined. Based on the microstructure of SLT, every stage of domain inversion in external field poling procedure at room temperature was discussed. According to the poling results, the functions between the parameters such as poling voltage and poling current were built. Theory of phase matching and quasi-phase matching is studied. Superlattice structure with wavelength of 3-5μm and its tuning mode are both designed with the consideration of SLT.Periodical polarization experiments were peformenced while the SLT crystal and poling equipment made by ourselves were uesed. In the experiments, metal electrodes, composite electrodes and liquid electrode were used. Based on the periodical poling results and domain reversion kinetics of SLT, the best electrode structure and poling curve were determined. PPSLT with 30μm periods was fabricated successfully.The interrelated basic theorics of the tunable mid-infrared OPO, such as the three wave interaction in the OPO or OPG,QPM theory,and the basic theory of the OPO have been analyzed and diseussed. How to design the OPO system based on PPSLT were introduced.A mid-infrared QPM OPO is demonstrated, in which a PPSLT crystal is pumped by a high-repetition all solid state Nd:YAG laser to realize the mid-infrared QPM OPO. The wavelength range of 3.34³.64μm is obtained through the temperature tuning, and when the average pump power is 7.5W, the average mid-infrared output power reaches 800mW.更多还原