分形超晶格结构晶体中的多波长频率转换  

Multi-wavelength Frequency Conversion in Fractal Superlattice Crystals

作　　者：王雪颖 马博琴[2] WANG Xueying;MA Boqin(School of Information and Communication Engineering,Communication University of China,Beijing 100024,China;School of Data Science and Intelligent Media,Communication University of China,Beijing 100024,China)

机构地区：[1]中国传媒大学信息与通信工程学院,北京100024 [2]中国传媒大学数据科学与智能媒体学院,北京100024

出　　处：《光子学报》2023年第11期113-121,共9页Acta Photonica Sinica

基　　金：校级科研项目(No.PT-11004175)。

摘　　要：非线性频率转换是非线性光学中的重点研究内容之一,本文将Gosper分形与Z分形两种超晶格结构引入非线性光子晶体中,理论分析了两种超晶格结构经过准相位匹配进行非线性频率转换的谐波特点。Gosper分形超晶格的倒空间结构整体旋转60°后,依然能够和原图形重合;在准相位匹配的条件下,能够在六个不同方向实现相同的倍频波长输出;在级联三倍频中,实现了波长为711.3 nm、554.7 nm、491 nm的三倍频输出,并理论计算了其偏离角度。在二维Z分形的傅里叶空间中,充分利用了高阶横向倒格矢,能够实现基波波长范围为1.402μm~1.430μm的二次谐波频率转换,其中波长间距最小仅有1 nm。最后,为三维Z分形超晶格结构晶体的制备提供了数据支持。Nonlinear frequency conversion is one of the key research contents in nonlinear optics.Using the external high voltage electric field poling technology to modulate the second-order nonlinear coefficient of nonlinear photonic crystals,quasi-phase-matching technology is commonly used to obtain efficient nonlinear frequency conversion.As the carrier of second-order nonlinear optical effects,optical superlattice is one of the important research topics in the field of nonlinear optics.In order to explore the advantages of different superlattice structures,more and more superlattice structures are applied to optical materials to generate harmonics of different wavelengths.Designing excellent optical superlattice structures to perform nonlinear frequency conversion has become the best solution to meet the needs of scientific research.Fractal superlattice structure has the advantage of relatively sparse arrangement in the real space and dense distribution in the reciprocal space.Therefore,fractal superlattice structure can provide highly efficient nonlinear interactions,and its advantage is more reflected in the higher-order frequency conversion.In this paper,Gosper fractal and Z fractal superlattice structures are introduced into nonlinear photonic crystals.In real space,Gosper fractal or Z fractal superlattice structure is composed of one continuous line.These two fractal superlattices can provide the complex spatial structure and rich reciprocal vectors.For Gosper fractal,it has six-fold rotational symmetry in the reciprocal space.It not only has the overall fractal dimension,but also has the boundary fractal dimension.For Z fractal,it has the periodic,quasi-periodic and fractal characteristics.The overall pattern gives the translational symmetry.The distributions of their reciprocal vectors are simulated by two-dimensional Fourier transform.The quasi-phase-matching harmonis in LiNbO3 nonlinear photonic crystals with these two superlattices are theoretically analyzed.Moreover,their diffraction experiments were carried

关 键 词：非线性光学 频率转换 准相位匹配 分形超晶格结构 倒易矢量 

分 类 号：O437[机械工程—光学工程]