基于零折射磁性特异电磁介质的波前调控

Manipulation of electromagnetic wavefront based on zero index magnetic metamaterial

本文基于二维磁性柱周期阵列设计了具有等效零折射率的磁性特异电磁介质.通过多重散射理论计算体系的光子能带和等效介质理论提取体系的等效电磁参量可以确定该磁性特异电磁介质可以实现等效介电常数和等效磁导率同时为零.利用该双零磁性特异电磁介质可以实现电磁波在无相位延迟下的传输,从而可以调控电磁波的空间相位变化.进而,通过设计具有不同电磁波输出界面的构型实现了高斯光束的波前由平面转变成柱面,还可以实现高斯光束的聚焦和高斯光束的分束.也可以根据需要设计具有更为一般的输出界面,实现更为多样的电磁波波前的调控.而且,磁性材料的电磁特性可以通过温度和外加磁场进行调制,因此该双零磁性特异电磁介质的工作频率可以灵活控制,这更便于电磁波器件的设计和应用.

In this work, a zero index magnetic metamaterial（ZIMM） is designed based on the two-dimensional array of ferrite rods periodically arranged in the air. By calculating the photonic band structures within the framework of multiple scattering theory and retrieving the effective electric permittivity εeffand effective magnetic permeability μeff, the structure parameters can be optimized and then the effectively matched zero index with εeff= μeff = 0 is achieved. Within this matched ZIMM, electromagnetic（EM） wave can propagate without any phase delay, resulting in the manipulation of phase pattern in space. By simulating the electric field patterns of a Gaussian beam incident on ZIMM slabs with different thickness, zero phase delay inside the slab can be observed. By designing various outgoing interfaces a plane EM wavefront can be transformed into a cylindrical one, or even into a more general wavefront. In addition, the focusing and beam splitting effects are demonstrated as well. Besides, since the permeability of magnetic materials can be controlled by an external magnetic field or a temperature, the EM features of ZIMM can be flexibly tuned, enabling a promising prospect in designing EM devices and potential applications.