离子束调控太赫兹光学材料的非线性性能研究

The nonlinear optical frequency conversion process around the wavelength of near infrared is an important strategy to generate coherent Terahertz radiation. This idea has been implemented in nonlinear optical systems based on gallium phosphide, gallium nitride and lithium niobate in order to generate Terahertz radiation. The quasi-phase-matching guarantee the high efficiency of nonlinear optical frequency conversion. The optical intensity can be enhanced in the waveguide structure hence the efficiency of Terahertz generation. Therefore Terahertz resource with high conversion efficiency and small size can be expected if the quasi-phase-matching can be achieved in the waveguide structure. Damage and defects with different types can be introduced into optical materials by means of ion irradiation. As a result, the microstructure hence the physical and chemical properties of implanted region can be altered at the same time. The quasi-phase-matching can be fabricated by using the ion irradiation with appropriate species, energy and fluence. Based on the former experience and achievements of ion implanted optical waveguide, we will invesitigate the ion irradation induced modulation effect of second order nonlinear optical properties in several Terahertz optical materials and unclose the hiding machanism. Our results can be used in the fabrication of quasi-phase-matching structure in the Terahertz optical waveguide and the realization of Terahertz resource with small size and its optical integration. This investigation also expand the application of the nuclear technology into domain of material science and nonlinear optics.

近红外激光的非线性光学频率转换是产生相干太赫兹辐射的重要方法。这种方法在磷化镓、氮化镓以及铌酸锂体材料中都取得了成功。准相位匹配是在材料中实现高效非线性光学频率转换的关键。波导结构可以大大提高光在材料中的光密度进而提高太赫兹辐射的效率。将准相位匹配和波导结构结合是实现太赫兹辐射源小型化的有效手段。离子辐照通过在材料中产生损伤及缺陷来诱导材料的微观结构发生变化，进而改变注入区域非线性光学性质，具有实现准相位匹配结构的潜力。本项目利用离子辐照在材料表面改性中的优势，结合已有的研究结果和经验，开展离子辐照调控太赫兹光学材料非线性性质的研究，深入探讨离子辐照调控材料非线性性质的物理机制，优化条件，制备出工作在THz波段的准相位匹配结构，为太赫兹辐射源的小型化及光子集成提供研究基础，拓展核技术在材料科学和非线性光学领域的应用。

红外非线性晶体可以产生并探测太赫兹辐射，在科研、商用及国防领域都具有应用前景。二十一世纪初已经有利用砷化镓、铌酸锂等非线性晶体产生或者探测太赫兹的报告。本项目主要利用离子束对铌酸锂，磷酸钛氧钾等非线性晶体晶体表面进行改性，对注入损伤造成的非线性系数进行探测，对其深度分布进行评价。研究离子注入对材料非线性性能的影响，明晰离子束调控其非线性性能的物理机制。本项目先后研究了重要的红外晶体，铌酸锂以及磷酸钛氧钾离子注入后的二阶非线性系数的深度分布。项目的研究结果在铌酸锂及磷酸钛氧钾上利用离子束技术形成准相位匹配结构提供实验基础和理论依据。