1.064μm激光大气斜程散射建模及仿真

为了研究大气气溶胶对激光斜程传输的散射特性,建立了基于米氏散射理论的1.064μm激光大气斜程散射模型。利用MATLAB软件对模型进行仿真计算,分析了斜程散射光辐射参量的分布特性。并结合地面探测分析了探测器的方位及探测方向对散射光辐射照度的影响。结果表明,该模型为机载激光指示器系统的战术训练、地面激光探测提供了可靠的理论依据。     

Numerical calculation of apparent IR radiation of cloud

The infrared detection has been one of important approaches for aerial target detection, but the existence of clouds in the sky makes target detection difficult, so it is of great significance to research the features of infrared radiation of clouds. Combining Mie scattering theory, the calculation model of infrared radiation on the cloud appearance was put forward and this model mainly considered two parts including direct and scattering radiation. The calculation methods of direct radiation, primary scattering and multiple scattering were discussed in detail to put forward the specific methods for numerical computation. Based on the calculation model, cumulus was taken as the example to calculate its radiation of wave band of long-wave infrared and analyze its radiation characters. The calculation results showed that: both perpendicular incidence and scattering could make great contributions to apparent radiation of cloud and could not be ignored; as for the distribution of direction angles, the radiation of clouds decreased with increase of direction angles as a whole; in the aspect of spectrum distribution, spectral radiance feature of the clouds was complicated function of wave length. Finally, the calculation results were verified using clouds imaging experiment of which the result also effectively proved the correctness of the calculation model.     

Control of light scattering by nanoparticles with optically-induced magnetic responses

Conventional approaches to control and shape the scattering pattems of light generated by different nanostructures are mostly based on engineering of their electric response due to the fact that most metallic nanostructures support only electric resonances in the optical frequency range. Recently, fuelled by the fast development in the fields of metamaterials and plasmonics, artificial optically-induced magnetic responses have been demonstrated for various nanostructures. This kind of response can be employed to provide an extra degree of freedom for the efficient control and shaping of the scattering patterns of nanoparticles and nanoantennas. Here we review the recent progress in this research direction of nanoparticle scattering shaping and control through the interference of both electric and optically-induced magnetic responses. We discuss the magnetic resonances supported by various structures in different spectral regimes, and then summarize the original results on the scattering shaping involving both electric and magnetic responses, based on the interference of both spectrally separated （with different resonant wavelengths） and overlapped dipoles （with the same resonant wavelength）, and also other higher-order modes. Finally, we discuss the scattering control utilizing Fano resonances associated with the magnetic responses.     

Latest achievements in generalized Lorenz‐Mie theories: A commented reference database

Generalized Lorenz‐Mie theories form a set of analytical approaches dealing with the interaction between electromagnetic arbitrary shaped beams and a class of particles possessing enough symmetries to allow one to use the method of separation of variables. This paper provides a commented reference database concerning generalized Lorenz‐Mie theories for the period 2009‐2013.     

Nd~(3+)掺杂硫系玻璃微球荧光腔量子电动力学增强效应

采用粉料漂浮高温熔融法自制Nd3+掺杂硫系玻璃微球,研究了腔量子电动力学增强效应对稀土掺杂硫系玻璃微球荧光光谱的影响。把直径90.53μm的硫系玻璃微球与锥腰直径1.02μm的石英光纤锥耦合,将808nm抽运激光导入微球,荧光光谱存在分立的共振峰。根据米氏散射理论公式,计算得到TE偏振态下基模的三个共振峰位置,确定了这三个共振峰的模式序数。增强因子η≈1122,这表明微球荧光自发辐射速率增强幅度为1122倍。在基模条件下对原增强因子公式进行近似化简,并利用近似公式进行估算得到η≈1167,误差为4%。     

太赫兹波在雾中的多重散射特性

太赫兹(THz)波作为微波和毫米波的延伸,它所提供的通信带宽和容量远大于毫米波。在随机介质中传播时,不但会发生时域和空域的形变,介质中的粒子还会对入射波发生散射,这些都会使得脉冲信号发生衰减。根据Mie理论与随机离散分布粒子的波传播与散射理论,计算了THz波信号入射下雾滴粒子的消光系数。结合雾滴粒子谱分布,得到了雾媒质的平均体系散射特性,采用蒙特卡罗法得到了平流雾对THz信号的多重散射特性,计算了THz波段信号对平流雾的透过率与反射率,分析了THz波段信号的前向、后向散射特性随散射角的分布。结果表明,低能见度大气环境中,雾对THz波产生的吸收和衰减不容忽视。相关研究结果对THz在大气传输、通信等方面的应用具有重要意义。     

基质折射率对反常色散散射体散射特性的影响

基于Mie散射理论,给出了散射强度、散射截面及吸收截面的计算公式,并对不同基质中碳化硅材料在反常色散区中的散射特性进行了数值计算与理论分析。结果表明,在反常色散区中,随着基质折射率的增大,散射强度的峰位发生红移,峰值增大;散射截面和吸收截面的峰位发生红移,峰值减小,这为该材料在反常色散区中的光学理论、实验及应用方面提供了理论参考。     

近距云雾回波蒙特卡罗模拟与实验测量

在激光引信中,云雾后向散射会产生引发虚警的回波信号。基于蒙特卡罗法对云雾回波信号进行了模拟仿真,并在云雾室内开展了测量实验,利用测量结果对理论模型进行了验证。研究结果表明:当发射脉冲宽度小于10 ns时,云雾散射回波展宽效应显著,且展宽效应主要是由多次散射产生的;激光回波的实验测量结果与理论计算结果吻合得较好,都近似为高斯波形,且其回波宽度的差别小于6%,回波功率差别小于30%。     

降雨对无线激光通信的影响

通过激光信号在雨介质中传输的实验发现,在大雨环境下,激光信号透射率要比在小雨或微雨的情况下大。这说明光信号在小雨时衰减较大,在大雨时衰减较小。这一现象与人们通常所认为的有所不同。针对降雨对激光信号的影响,根据Mie散射理论和Weibull雨滴尺寸分布模型,分析了不同尺寸的粒子对光的散射作用以及对衰减效率因子的影响,推导出单球粒子对光波的衰减公式,得到了衰减与降雨率的确定关系。通过数值计算发现,与小粒子相比大粒子的前向散射光强更大且更加集中;激光信号在雨介质中传输时,衰减系数在小雨时较大,中雨、大雨时较小,暴雨时不断增大。这一结果与实际情况较吻合,为激光在通信系统中的应用提供了一定的理论依据。     

Al_2O_3和MgO多粒子体系光学截面的计算

本文利用微粒子 Mie散射理论建立了混合多粒子体系的光散射模型 ,计算了相应模型下 Al2 O3和 Mg O的光学截面