Sasihithlu Karthik, Narayanaswamy Arvind
Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA.
Opt Express. 2011 Jul 4;19 Suppl 4:A772-85. doi: 10.1364/OE.19.00A772.
Near-field radiative transfer between two objects can be computed using Rytov's theory of fluctuational electrodynamics in which the strength of electromagnetic sources is related to temperature through the fluctuation-dissipation theorem, and the resultant energy transfer is described using the dyadic Green's function of the vector Helmholtz equation. When the two objects are spheres, the dyadic Green's function can be expanded in a series of vector spherical waves. Based on comparison with the convergence criterion for the case of radiative transfer between two parallel surfaces, we derive a relation for the number of vector spherical waves required for convergence in the case of radiative transfer between two spheres. We show that when electromagnetic surface waves are active at a frequency the number of vector spherical waves required for convergence is proportional to Rmax/d when d/Rmax → 0, where Rmax is the radius of the larger sphere, and d is the smallest gap between the two spheres. This criterion for convergence applies equally well to other near-field electromagnetic scattering problems.
两个物体之间的近场辐射传输可以使用里托夫波动电动力学理论来计算。在该理论中，电磁源的强度通过涨落耗散定理与温度相关，并且使用矢量亥姆霍兹方程的并矢格林函数来描述由此产生的能量传输。当两个物体为球体时，并矢格林函数可以展开为一系列矢量球面波。基于与两个平行表面之间辐射传输情况的收敛准则进行比较，我们推导出了两个球体之间辐射传输收敛所需的矢量球面波数量的关系。我们表明，当电磁表面波在某一频率下活跃时，收敛所需的矢量球面波数量在(d/R_{max}→0)时与(R_{max}/d)成正比，其中(R_{max})是较大球体的半径，(d)是两个球体之间的最小间距。该收敛准则同样适用于其他近场电磁散射问题。
