光频段双层手征结构光学特性及负折射率研究

设计了一种工作在光波段的新型四重对称的双层手征结构,通过数值模拟得到透射系数和反射系数,反演计算了结构的圆二色性、旋光角、手征参数和折射率。结果表明该结构在谐振波长附近具有很强的旋光性,并且在椭偏度为零时,即透射光变成完全线偏振光时,旋光角达到了55°;在一定波段内可以实现左旋圆偏振光(LCP)和右旋圆偏振光(RCP)的负折射率,且不需要介电常数和磁导率同时为负,更重要的是,实现负折射率的左旋圆偏振光(LCP)具有较宽的频带,不局限于谐振波长附近,在椭偏度为零时,折射率也为负。考虑到具体的实验制作,对加衬底的手征结构进行了数值模拟,结果表明谐振波长向长波长方向产生了偏移,完全线性偏振光的旋光角仍然有40°。     

A planar chiral nanostructure with asymmetric transmission of linearly polarized wave and huge optical activity in near-infrared band

Just like an electronic diode that allows the electrical current to flow in one direction only, a kind of chiral metamaterial structure with a similar functionality for the electromagnetic wave is proposed. The designed nanostructure that consists of twisted metallic split-ring resonators on both sides of a dielectric substrate achieves asymmetric transmission for a forward and backward propagating linearly polarized wave by numerical simulation in near-infrared band. Difference in transmission efficiency of the optimized structure between the same polarized waves incident from opposite directions can reach a maximum at the communication wavelength （1.55 μm）. Moreover, the simulation results of this structure also exhibit strong optical activity and circular dichroism.     

Design of two-dimensional elliptically cylindrical invisible cloaks with multiple regions

Two-dimensional(2D) elliptically cylindrical invisible cloaks with multiple regions are designed based on the transformation optics and the complementary media theory. Multiple invisible cloak regions can be obtained by properly using the compressed or folded transformation in each space layer. The constitutive parameter tensor expressions for each region have been obtained. The results of full wave simulations by using finite element software confirm the validity of the constitutive parameter tensor expressions. In addition, the parameters are relatively easier to realize.     

二维椭圆形散射转移斗篷的设计研究

基于变换光学理论设计了椭圆形散射转移斗篷,并推导了相应的本构参数张量表达式,根据得到的本构参数,利用基于有限元算法的软件分别对椭圆形介质柱、导体柱进行了全波仿真验证.仿真结果证实了所得本构参数的正确性,验证了散射转移斗篷可以模拟任意物体,包括介质、导体的幻象,这些结果为设计隐身斗篷提供了一种新的理论途径.     

基于线变换的椭圆柱外隐身斗篷的设计研究

基于线变换方法与互补媒质理论提出了线变换下的椭圆柱外隐身斗篷,并得到了相应外隐身斗篷材料本构参数张量的表达式.根据导出的本构参数张量,利用电磁仿真软件分别对不同长度线段的外斗篷进行了仿真验证,仿真结果证实了所得到的本构参数张量的正确性.这种外斗篷的材料参数只在轴向变化,横向参数为常数,易于用超介质制备.考虑到损耗对隐身效果的影响,得到了引入损耗后的外斗篷磁场分布.最后给出了本构参数的分布.本文的研究为利用超介质制备外隐身斗篷提供了一种新的可行的方法.