Orbital angular momentum (OAM) spectrum diagnosis is a fundamental building block for diverseOAM-based systems. Among others, the simple on-axis interferometric measurement can retrieve theamplitude and phase informat...Orbital angular momentum (OAM) spectrum diagnosis is a fundamental building block for diverseOAM-based systems. Among others, the simple on-axis interferometric measurement can retrieve theamplitude and phase information of complex OAM spectra in a few shots. Yet, its single-shot retrievalremains elusive, due to the signal–signal beat interference inherent in the measurement. Here, weintroduce the concept of Kramers–Kronig (KK) receiver in coherent communications to the OAM domain,enabling rigorous, single-shot OAM spectrum measurement. We explain in detail the working principle andthe requirement of the KK method and then apply the technique to precisely measure variouscharacteristic OAM states. In addition, we discuss the effects of the carrier-to-signal power ratio and thenumber of sampling points essential for rigorous retrieval and evaluate the performance on a large set ofrandom OAM spectra and high-dimensional spaces. Single-shot KK interferometry shows enormouspotential for characterizing complex OAM states in real time.展开更多
Epitaxial BaTiO3 films with embedded metallic Ni nanocrystal （Ni-BaTiO3） were successfully fabricated on SrTiO3 （001） single-crystalline substrate through the laser molecular beam epitaxial （L-MBE） technique.Hig...Epitaxial BaTiO3 films with embedded metallic Ni nanocrystal （Ni-BaTiO3） were successfully fabricated on SrTiO3 （001） single-crystalline substrate through the laser molecular beam epitaxial （L-MBE） technique.High resolution transmission electron microscopy （HRTEM） and electron energy loss spectrum （EELS） with Kramers-Kronig analysis methods were employed to characterize the microstructures,elementary distribution and the electron structure of these films.HRTEM results suggested that the structure of BaTiO3 was tetragonal with lattice parameters of a=0.399 nm and c=0.403 nm.Energy dispersive X-Ray spectroscopy （EDX） confirmed metallic Ni nanocrystal embedded successfully in BaTiO3 epitaxial films.The Ni-BaTiO3 composite films were compound of the epitaxial BaTiO3 （110） layers alternating with Ni NCs array （111） layers.Furthermore,the existence of the misfit dislocations induced by the embedding of Ni nanoparticles was also clearly demonstrated by the HRTEM images.The Ni L2,3 edges of EELS revealed that Ni NCs in their metallic state were embedded uniformly in the BaTiO3 matrix.A chemical shift of about 7 eV regarding L3 edges in the Ni EELS was also observed.The optical band gap of BaTiO3 in these films was about 3.84 eV,higher than 3.55 eV for pure BaTiO3 films at room temperature.展开更多
The expanded graphite (EG) with a low density and better extinction performance can be used in military as passive jamming material in IR and MMW bands. Its complex refractive index is a significant parameter for the ...The expanded graphite (EG) with a low density and better extinction performance can be used in military as passive jamming material in IR and MMW bands. Its complex refractive index is a significant parameter for the extinction property. This paper presents a method to calculate the complex refractive index of EG. The reflection spectra of EG pellets were measured in the 0.24-2.6μm and 2.5-25μm bands, respectively. Based on the measurement results, the complex refractive index of EG in 5-10μm band was calculated by using Kramers-Kronig(K-K) relation and Bruggeman effective medium theory, and then the errors were analyzed. The results indicate that it is feasible to calculate the complex refractive index of EG based on its IR reflection spectra data.展开更多
We measure the absorption and dispersion in a Doppler-broadened A-type three level system by resonant stimulated Raman spectroscopy with homodyne detection. Through studying the dressed state energies of the system, i...We measure the absorption and dispersion in a Doppler-broadened A-type three level system by resonant stimulated Raman spectroscopy with homodyne detection. Through studying the dressed state energies of the system, it is found that the absorption and dispersion satisfy the Kramers-Kronig relation. The absorption and dispersion spectra calculated by employing this relation agree well with our experimental observations.展开更多
A parameter retrieval algorithm based on the causality principle and Kramers-Kronig （KK） relations is employed to calculate the effective parameters of three-dimensional （3D） metamaterials. Using KK relations, the...A parameter retrieval algorithm based on the causality principle and Kramers-Kronig （KK） relations is employed to calculate the effective parameters of three-dimensional （3D） metamaterials. Using KK relations, the branch selecting problem, which is the challenge of effective parameter retrieval method, can be removed. To reveal the validity of the proposed algorithm, the constitutive refractive index of a homogeneous polymide cube is extracted. The result is in excellent agreement with the intrinsic refractive index of the polymide. Finally, the two terahertz metamaterials with 3D structures are designed and their effective parameters are then retrieved using the proposed algorithm. Numerical simulations are performed using the fuiI-wave electromagnetic solver, CST Microwave Studio.展开更多
The photoabsorption cross sections of condensed atoms and molecules have proven to be dependent not only on the imaginary parts but also on the real parts of the polarizabilities due to the strong interatomie interact...The photoabsorption cross sections of condensed atoms and molecules have proven to be dependent not only on the imaginary parts but also on the real parts of the polarizabilities due to the strong interatomie interactions in condensed environment. The real parts of the polarizabilities calculated usually by using the famous Kramers-Kronig transformation （KKT） from the photoabsorption cross sections of the isolated atoms are very sensitive to the accuracy of the implementation method of the infinite integral in the KKT. The influence of the integral instability of the KKT and the real part of the polarizability on the variation of the photoabsorption cross sections with the number density and the structure of the condensed matter has been studied in the present work for the first time. The conclusion is that the integration method with interpolation has given more reasonable results than the direct truncation method if some appropriate interpolation functions have been used. Some notes and conclusions have also been given for the applications of the alternative coupled expressions of photoabsorption cross sections.展开更多
为了更好地描述沥青混合料的时间和温度依赖性,优选表征动态力学性质的黏弹力学模型,推广黏弹性动态力学设计方法。基于线性黏弹性Kramers-Kronig近似解析式,通过对存储模量Sigmoidal函数解析式求导后,得到损失模量解析式,称为Sigmoida...为了更好地描述沥青混合料的时间和温度依赖性,优选表征动态力学性质的黏弹力学模型,推广黏弹性动态力学设计方法。基于线性黏弹性Kramers-Kronig近似解析式,通过对存储模量Sigmoidal函数解析式求导后,得到损失模量解析式,称为SigmoidalⅡ类模型。应用黏弹性材料时-温等效原理,通过构造不同目标函数,建立了上述模型黏弹函数主曲线,并与SigmoidalⅠ-Ⅰ模型、SigmoidalⅠ-Ⅱ模型进行了对比分析。结果表明:3个模型均能应用时-温等效原理建立黏弹函数(动态模量和相位角)的主曲线,与AASHTO R 62-131规范对比,3个模型均提出了相位角主曲线解析式,目标函数构造时,黏弹参数的选择影响Sigmoidal模型的拟合效果。对比另外2个模型,SigmoidalⅡ模型仅采用一个黏弹参数(动态模量)构造目标函数即可建立所有黏弹参数主曲线及Cole-Cole曲线,且黏弹函数测试值与预测值吻合较好,其中,动态模量和相位角曲线的拟合优度均在0.95以上,说明该模型能更好地描述沥青混合料的动态黏弹参数。SigmoidalⅡ模型存储模量和损失模量(动态模量和相位角)共用一套模型参数,黏弹参数之间满足线性黏弹性因果关系且符合力学模型的要求。SigmoidalⅡ模型可为沥青混合料设计和沥青路面层状黏弹动力学计算提供新的参考。展开更多
基金supported by the National Key Research and Development Program of China (2018YFB1801803, 2019YFA0706302)the Basic and Applied Basic Research Foundation of Guangdong Province (2021B1515020093, 2021B1515120057)+1 种基金the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X121)the Swiss National Science Foundation (P2ELP2_199825)
文摘Orbital angular momentum (OAM) spectrum diagnosis is a fundamental building block for diverseOAM-based systems. Among others, the simple on-axis interferometric measurement can retrieve theamplitude and phase information of complex OAM spectra in a few shots. Yet, its single-shot retrievalremains elusive, due to the signal–signal beat interference inherent in the measurement. Here, weintroduce the concept of Kramers–Kronig (KK) receiver in coherent communications to the OAM domain,enabling rigorous, single-shot OAM spectrum measurement. We explain in detail the working principle andthe requirement of the KK method and then apply the technique to precisely measure variouscharacteristic OAM states. In addition, we discuss the effects of the carrier-to-signal power ratio and thenumber of sampling points essential for rigorous retrieval and evaluate the performance on a large set ofrandom OAM spectra and high-dimensional spaces. Single-shot KK interferometry shows enormouspotential for characterizing complex OAM states in real time.
基金Funded by National High Technology Research and Development Program of China (863 Program)
文摘Epitaxial BaTiO3 films with embedded metallic Ni nanocrystal （Ni-BaTiO3） were successfully fabricated on SrTiO3 （001） single-crystalline substrate through the laser molecular beam epitaxial （L-MBE） technique.High resolution transmission electron microscopy （HRTEM） and electron energy loss spectrum （EELS） with Kramers-Kronig analysis methods were employed to characterize the microstructures,elementary distribution and the electron structure of these films.HRTEM results suggested that the structure of BaTiO3 was tetragonal with lattice parameters of a=0.399 nm and c=0.403 nm.Energy dispersive X-Ray spectroscopy （EDX） confirmed metallic Ni nanocrystal embedded successfully in BaTiO3 epitaxial films.The Ni-BaTiO3 composite films were compound of the epitaxial BaTiO3 （110） layers alternating with Ni NCs array （111） layers.Furthermore,the existence of the misfit dislocations induced by the embedding of Ni nanoparticles was also clearly demonstrated by the HRTEM images.The Ni L2,3 edges of EELS revealed that Ni NCs in their metallic state were embedded uniformly in the BaTiO3 matrix.A chemical shift of about 7 eV regarding L3 edges in the Ni EELS was also observed.The optical band gap of BaTiO3 in these films was about 3.84 eV,higher than 3.55 eV for pure BaTiO3 films at room temperature.
文摘The expanded graphite (EG) with a low density and better extinction performance can be used in military as passive jamming material in IR and MMW bands. Its complex refractive index is a significant parameter for the extinction property. This paper presents a method to calculate the complex refractive index of EG. The reflection spectra of EG pellets were measured in the 0.24-2.6μm and 2.5-25μm bands, respectively. Based on the measurement results, the complex refractive index of EG in 5-10μm band was calculated by using Kramers-Kronig(K-K) relation and Bruggeman effective medium theory, and then the errors were analyzed. The results indicate that it is feasible to calculate the complex refractive index of EG based on its IR reflection spectra data.
基金supported by the National Basic Research Program of China(Grant Nos.2013CB922002 and 2010CB922904)the National Natural Science Foundation of China(Grant Nos.11274376 and 61308011)the Natural Science Foundation of Hebei Province,China(Grant No.A2015205161)
文摘We measure the absorption and dispersion in a Doppler-broadened A-type three level system by resonant stimulated Raman spectroscopy with homodyne detection. Through studying the dressed state energies of the system, it is found that the absorption and dispersion satisfy the Kramers-Kronig relation. The absorption and dispersion spectra calculated by employing this relation agree well with our experimental observations.
文摘A parameter retrieval algorithm based on the causality principle and Kramers-Kronig （KK） relations is employed to calculate the effective parameters of three-dimensional （3D） metamaterials. Using KK relations, the branch selecting problem, which is the challenge of effective parameter retrieval method, can be removed. To reveal the validity of the proposed algorithm, the constitutive refractive index of a homogeneous polymide cube is extracted. The result is in excellent agreement with the intrinsic refractive index of the polymide. Finally, the two terahertz metamaterials with 3D structures are designed and their effective parameters are then retrieved using the proposed algorithm. Numerical simulations are performed using the fuiI-wave electromagnetic solver, CST Microwave Studio.
基金Supported by the Natural Science Foundations of Ludong University under Grant Nos.22270301 and L20072804
文摘The photoabsorption cross sections of condensed atoms and molecules have proven to be dependent not only on the imaginary parts but also on the real parts of the polarizabilities due to the strong interatomie interactions in condensed environment. The real parts of the polarizabilities calculated usually by using the famous Kramers-Kronig transformation （KKT） from the photoabsorption cross sections of the isolated atoms are very sensitive to the accuracy of the implementation method of the infinite integral in the KKT. The influence of the integral instability of the KKT and the real part of the polarizability on the variation of the photoabsorption cross sections with the number density and the structure of the condensed matter has been studied in the present work for the first time. The conclusion is that the integration method with interpolation has given more reasonable results than the direct truncation method if some appropriate interpolation functions have been used. Some notes and conclusions have also been given for the applications of the alternative coupled expressions of photoabsorption cross sections.
文摘为了更好地描述沥青混合料的时间和温度依赖性,优选表征动态力学性质的黏弹力学模型,推广黏弹性动态力学设计方法。基于线性黏弹性Kramers-Kronig近似解析式,通过对存储模量Sigmoidal函数解析式求导后,得到损失模量解析式,称为SigmoidalⅡ类模型。应用黏弹性材料时-温等效原理,通过构造不同目标函数,建立了上述模型黏弹函数主曲线,并与SigmoidalⅠ-Ⅰ模型、SigmoidalⅠ-Ⅱ模型进行了对比分析。结果表明:3个模型均能应用时-温等效原理建立黏弹函数(动态模量和相位角)的主曲线,与AASHTO R 62-131规范对比,3个模型均提出了相位角主曲线解析式,目标函数构造时,黏弹参数的选择影响Sigmoidal模型的拟合效果。对比另外2个模型,SigmoidalⅡ模型仅采用一个黏弹参数(动态模量)构造目标函数即可建立所有黏弹参数主曲线及Cole-Cole曲线,且黏弹函数测试值与预测值吻合较好,其中,动态模量和相位角曲线的拟合优度均在0.95以上,说明该模型能更好地描述沥青混合料的动态黏弹参数。SigmoidalⅡ模型存储模量和损失模量(动态模量和相位角)共用一套模型参数,黏弹参数之间满足线性黏弹性因果关系且符合力学模型的要求。SigmoidalⅡ模型可为沥青混合料设计和沥青路面层状黏弹动力学计算提供新的参考。
