The optical constants of fiber materials are of great value in the study of the mechanism and application of radiation regulation, but the conventional methods for obtaining the optical constants of fiber materials suffer from a series of problems such as compositional differences, chemical residues, and microstructural damages, which make it difficult to obtain the optical constants of the fiber materials and make the final results of the measurements doubtful. In this work, a new intelligent inversion method is developed, based on the first-principles calculations of electromagnetic scattering using Finite Difference Time Domain method and particle swarm optimization algorithm (FDTD-PSO), to obtain the optical constants of fibers through the measurement of the scattered radiation properties of fiber materials and the characterization of their surface microstructures. The feasibility and accuracy of the method are demonstrated by theoretical numerical calculation simulations of different kinds of fibers, and the scale effect and error are analyzed from three aspects, namely, scale parameters, roughness and incident light angle direction. The results show that the dimensions, roughness and incident wavelength of the fiber material are in the sub-wavelength scale interval, which requires high model accuracy and gives the appropriate inversion range interval. Finally, the method is experimentally validated by using the natural silk fibers. This work constructs a complete set of theoretical models and experimental methods to accurately obtain the optical constants of actual fiber materials, which provides a new direction for obtaining the optical constants of fiber materials and a numerical basis for the study of the radiation modulation mechanism of fiber materials.

中文翻译：

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基于FDTD-PSO和散射实验的天然丝纤维光学常数反演


纤维材料的光学常数在研究辐射调控的机理和应用方面具有重要价值，但获取纤维材料光学常数的常规方法存在成分差异、化学残留、微观结构损伤等一系列问题，难以获得纤维材料的光学常数，使最终测量结果存疑。本工作基于有限差分时域法和粒子群优化算法 （FDTD-PSO） 的电磁散射第一性原理计算，开发了一种新的智能反演方法，通过测量光纤材料的散射辐射特性并表征其表面微观结构来获得光纤的光学常数。通过对不同种类纤维的理论数值计算模拟，证明了该方法的可行性和准确性，并从尺度参数、粗糙度和入射光角度方向3个方面分析了尺度效应和误差。结果表明，纤维材料的尺寸、粗糙度和入射波长均处于亚波长尺度区间内，对模型精度要求较高，并给出了合适的反演范围区间。最后，利用天然蚕丝纤维对该方法进行了实验验证。本工作构建了一整套精确获取实际光纤材料光学常数的理论模型和实验方法，为获取纤维材料的光学常数提供了新的方向，为研究纤维材料的辐射调制机理提供了数值基础。