All-dielectric left-handed metamaterial based on dielectric resonator: design, simulation and experiment

Dipoles with Lorentz-type resonant electromagnetic responses can realise negative effective parameters in their negative resonant region. The electric dipole and magnetic dipole can realise, respectively, negative permittivity and negative permeability, so both the field distribution forms of electric and magnetic dipoles are fundamentals in designing left-handed metamaterial. Based on this principle, this paper studies the field distribution in high-permittivity dielectric materials. The field distributions at different resonant modes are analysed based on the dielectric resonator theory. The origination and influence factors of the electric and magnetic dipoles are confirmed. Numerical simulations indicate that by combining dielectric cubes with different sizes, the electric resonance frequency and magnetic resonance frequency can be superposed. Finally, experiments are carried out to verify the feasibility of all-dielectric left-handed metamaterial composed by this means.     

Dual-band frequency selective surface with large band separation and stable performance

A new technique of designing a dual-band frequency selective surface with large band separation is presented.This technique is based on a delicately designed topology of L-and Ku-band microwave filters.The two band-pass responses are generated by a capacitively-loaded square-loop frequency selective surface and an aperture-coupled frequency selective surface,respectively.A Faraday cage is located between the two frequency selective surface structures to eliminate undesired couplings.Based on this technique,a dual-band frequency selective surface with large band separation is designed,which possesses large band separation,high selectivity,and stable performance under various incident angles and different polarizations.     

A Method of Analyzing Transmission Losses in Left-Handed Metamaterials

A method of analyzing transmission loss in left-handed metamaterials （LHMs） is proposed. As a demonstration of this method, transmission loss of LHMs composed of split-ring resonators （SRR） and conducting wires is studied. By means of retrieving and analyzing the effective constitutive parameters, different transmission losses as well as their origins are studied. The results show that the left-handed bandwidth is narrowed because of high loss caused by the non-zero high imaginary parts of the effective permeability and permittivity. In the effective left-handed band, the radiation loss is very low and can be neglected, and the transmission losses are the sum of the substrate loss and the ohmic loss. Moreover, when the dielectric loss tangent of the substrate is greater than 0.003, the substrate loss is higher than the ohmic loss.     

外加电场法制备LiNbO3周期畴的反转电流特性研究

采用外加电场法制备了LiNbO₃单晶周期畴结构. 在对不同尺寸周期畴的反转电流进行比较研究的基础上,提出了一种确定反转畴成核时间和纵向贯穿速率的方法. 根据这一方法,得到在电场强度为25.1kV/mm,脉冲宽度为50 ms的脉冲方波作用下,LiNbO₃单晶反转畴的成核时间约为80ns,纵向贯穿速率约为0.1667m/s. 关键词： 3单晶周期极化')" href="#">LiNbO₃单晶周期极化 反转电流 反转畴成核时间 反转畴纵向贯穿速率     

The design of metamaterial cloaks embedded in anisotropic medium

By using coordinate transformation method, this paper obtains an useful equation of designing meta-material cloaks embedded in anisotropic medium. This equation is the generalization of what was introduced early by Pendry et al (2006 \textit{Science} {312 1780) and can be more widely used. As an example of its applications, this paper deduces the material parameter equation for cylinder cloaks embedded in anisotropic medium, and then offers the numerical simulation. The results show that such a cylinder cloak has perfect cloaking performance and therefore verifies the method proposed in this paper.     

Material parameter equation for rotating elliptical spherical cloaks

By using the coordinate transformation method, we have deduced the material parameter equation for rotating elliptical spherical cloaks and carried out simulation as well. The results indicate that the rotating elliptical spherical cloaking shell, which is made of meta-materials whose permittivity and permeability are governed by the equation deduced in this paper, can achieve perfect invisibility by excluding electromagnetic fields from the internal region without disturbing any external field.     

一种极化不敏感和双面吸波的手性超材料吸波体

基于手性结构设计了一种极化不敏感和双面吸波的超材料吸波体.该吸波体的结构单元由手性结构和介质基板组成.仿真的电磁波正、反向入射时超材料吸波体的吸收率表明:该吸波结构的正、反面是互易的,具有双面吸波特性.仿真的不同极化角下超材料吸波体的吸收率表明:该超材料吸波体具有极化不敏感特性.仿真的不同入射角下超材料吸波体的吸收率表明:该超材料吸波体的入射角较窄.仿真的吸波体单元的表面电流和磁能密度分布表明:电、磁场之间存在交叉耦合,吸波与手性有关.仿真的不同损耗情况下超材料吸波体的吸收率表明:基板的介质损耗在吸波过程中起主导作用,金属的电阻热可以忽略不计.该超材料吸波体可能在要求双面吸波的领域中具有潜在的应用. 关键词： 极化不敏感 双面吸波 手性结构 超材料吸波体     

铌酸钾钠基无铅透明陶瓷制备及性能

采用传统固相烧结工艺, 结合特殊的气氛控制技术,制备了铌酸钾钠(KNN)基无铅透明陶瓷 xBa(Sc_0.5Nb_0.5)O₃-(1-x) (K_0.5N_0.5)NbO₃ (简写xBSN-(1-x)KNN). 并对其微观结构、介电、铁电性能和光学透光率进行了研究. 结果表明该体系陶瓷具有准立方钙钛矿结构, 没有其他杂相, 晶粒大小与可见光波长相当, 高度致密, 无明显的晶界存在. 在 x=0.05时, d₃₃最高可达到110 pC/N, 2P_r达到25.4 μC/cm². 同时该材料具有良好的透明性, 在可见光范围内,透过率达到54%左右, 近红外2500 nm处,透过率接近83%, 是一种有望取代铅基透明陶瓷的环境友好型无铅透明陶瓷.     

电谐振器和磁谐振器构成的左手材料的实验验证

加工、制作和测试了由电谐振器和磁谐振器构成的左手材料.首先分别测试了电谐振器、磁谐振器各自的传输频谱,得到各自的负参数区域,然后测试了由电谐振器和磁谐振器构成的左手材料的传输频谱,并提取了其等效介电常数和磁导率.实验结果表明,在电谐振器和磁谐振器各自传输禁带的重合区域,出现了一个通带,在该通带内,等效介电常数和磁导率同时为负,验证了材料的左手特性.