相干散射机制对微纳无序介质中光子局域态密度的影响研究

Effect of Dependent Scattering on the Photonic Local Density of States(PLDOS) in Micro/Nanoscale Disordered Media

微纳无序介质中复杂的热辐射电磁波的多重散射现象,对光子局域态密度有着较大的影响,目前对该机制的研究尚较为欠缺。本文从数值计算和理论分析两方面入手,深入探究了微纳无序介质中的相干散射机制对其中光子局域态密度的影响。本文随机生成了硬球堆积结构,将散射体对电磁波的响应简化为偶极子,建立了耦合偶极子模型,对考虑多体散射的光子局域态密度进行严格求解。同时,本文基于准晶体近似,推导了考虑相干散射的光子局域态密度的理论计算公式,并与独立散射、Maxwell-Garnett等效介质理论进行了对比,结果表明,准晶体近似较为准确地考虑了随机介质中粒子排布的位置关联效应,从而对相干散射影响机制的估计更为准确。

The multiple scattering of radiation in micro/nanoscale disordered and porous media has a great impact on the photonic local density of states(PLDOS). Am in-depth investigation is still lacking. In this study, we numerically and theoretically explore the role of dependent scattering mechanism in PLDOS. We generate a hard-sphere random medium and treat the scatterers as electric dipoles, and a coupled-dipole model is established. Based on this model, we numerically calculate the PLDOS with considerations on the multiple scattering of electromagnetic waves. Afterwards, using the quasicrystalline approximation(QCA), we theoretically derive the formulism of PLDOS, and compare its prediction with those of independent scattering approximation(ISA) and Maxwell-Garnett effective medium theory. Results show that QCA can take the particle correlations into account and thus show a better agreement with numerical results.