非磁性小粒子散射的磁偶极贡献

Contribution to Magnetic Dipole due to the Scattering from Small Non-Magnetic Particles

采用磁偶极子和电四极子模型下的静场近似方法 ,得到了球形小粒子电磁散射场的两个高阶项 ,其大小正比于粒子半径的五次方 ,它和Mie级数解中对应的两项近似结果完全一致 ,从而可以将Mie级数解中这两项解释为磁偶极和电四极项散射的贡献。该方法仅要求粒子的几何尺寸的平方远小于波长的平方 ,在该条件下可将这种方法推广应用到非球形粒子 ,并给出了椭球和矩形两种非球形小粒子磁偶极散射贡献的理论计算公式 ,其结果与FDTD数值模拟结果有很好的一致性。

Using the static field approximation for the magnetic dipole and the electronic quadrupole models, two high order terms of the electromagnetic field scattered by a dielectric small spherical particle are obtained. They are proportional to the 5-th power of the radius and are consistent with the two counterpart terms of the Mie power series. Thus these two terms can be seen as the contribution of the magnetic dipole and the electronic quadrupole, respectively. The method requires that the square of the particle's radius is much smaller than the square of the wavelength. In this limitation the method can also be applied to non-spherical particles. The scattering contributions by the magnetic dipole for small ellipsoidal and rectangular particles are derived theoretically, which are well consistent with the FDTD numerical results.