摘要
设计了一种基于三维狄拉克半金属(DSM)动态可调谐的四频段太赫兹超材料窄带完美吸波器,在3.4695、4.3829、4.5790、4.9885 THz频率处实现4个吸收率接近100%的谐振峰。对谐振频率处的电磁场分布进行了数值研究,并结合阻抗匹配原理,定性地解释了吸收体完美吸收的物理机制。研究了单元结构尺寸和DSM费米能级对吸波特性的影响规律,证明了谐振峰频率和吸收率均具有良好的可调性。进一步地,当吸波器的工作环境折射率由1.00增加至1.16时,谐振频率红移且折射率响应灵敏度高达721.8 GHz·RIU^(-1)。在法向入射下,表现出与极化无关的吸收特性。本研究为THz吸波器及相关DSM器件研制提供参考,同时在多波段光电探测、生物传感和光学滤波等领域中具有很大的应用潜力。
Objective Terahertz(THz)absorbers are essential devices for suppressing electromagnetic interference or pollution in related THz system and play an increasingly important role in THz applications such as wireless communications,imaging,and sensing.Metamaterials,composed of artificially designed periodic subwavelength structure arrays,have the desired electromagnetic response beyond traditional materials.Since Landy et al.proposed the classical metamaterialinsulator-metal(MIM)absorber configuration,various THz absorbers integrating metamaterial and functional materials have been developed in both fundamental and applied research.Among them,graphene-based hybrid metamaterial THz absorbers have attracted wide attention due to their tunable transmission and flexible design.However,the natural optical properties of the ultrathin 2D graphene,like low absorption of incident waves and weak electromagnetic response,limit its applications in high-performance THz absorbers.The emerging 3D Dirac semimetal(DSM)exhibits high carrier mobility and tunable Fermi level comparable to graphene and overcomes the above-mentioned inherent disadvantages of graphene.In this study,a tunable four-band THz metamaterial absorber based on Dirac semimetal is designed.Using the finite integration method,the absorption characteristics in THz regime are systematically simulated in response to the structural parameters and Fermi levels of DSM.Methods We introduce a dynamically tunable four-band THz metamaterial perfect absorber based on a three-dimensional DSM.The designed MIM structure consists of DSM metamaterial layer,a dielectric layer,and a metal substrate layer from top to bottom(Fig.1).First,we calculate the Fermi level-dependent complex permittivity of 3D DSM in the frequency range of 3.0 THz to 5.2 THz based on the Kubo formula and the two-band model(Fig.2).Then,we perform finite-integration-method-based simulations to reveal electromagnetic field distribution and absorption spectra,and we simulate the absorption spectra of the two substructures of the rectangular ring and the circle separately.In addition,we discuss the effects of structural parameters and Fermi levels on spectral evolution and absorption properties.Results and Discussions From the electromagnetic field distribution,we can see that the strong magnetic resonance is mainly generated in the PI medium layer,while the electric resonance is dominantly excited on the surface of the DSM layer(Fig.4).Together,they give rise to the four-band near-perfect absorption of THz waves,and this can also be interpreted by the three equivalent sub-structure resonators(Fig.5).The absorption intensity and frequency remain stable when changing the structural parameters of R,W_(1),L_(1),and h_(2)within a small range(Fig.6).As the Fermi level of DSM increases from 50 meV to 75 meV,the frequencies of the resonant peaks M_(1)-M_(4)show a blue-shift trend,and the corresponding frequency shifts are 110.5,99.6,45.0,and 85.5 GHz,respectively(Fig.7).Meanwhile,the absorption intensities are relatively high with a value above 95%.By tuning the surrounding refractive index(RI)from 1.00 to 1.16,a maximum sensitivity up to 721.8 GHz·RIU-1 can be obtained(Fig.8).Conclusions We demonstrate a tunable THz metamaterial absorber based on 3D DSM through numerical simulations.The simulated electromagnetic field distributions and the impedance-matching analysis at the resonant frequency suggest that the perfect multi-band absorption is induced by the electric resonance excited on the DSM layer and the strong magnetic resonance formed in the PI layer.The resonant frequency and absorptivity show good tunability as the Fermi level of DSM changes from 50 meV to 75 meV.There is a linear relation between the resonant frequency and the surrounding refractive index,leading to a large sensitivity of 721.8 GHz·RIU-1 in the RI sensing range of 1.00 to 1.16.Furthermore,the absorption properties are proved to be insensitive to the polarization angle of incident THz wave.These findings not only provide an important reference for the development of 3D DSM based absorbers but also pave the way for the potential applications of tunable and broadband THz devices.
作者
张晶晶
张桂才
宋效先
张海婷
梁莹
戴子杰
姚建铨
Zhang Jingjing;Zhang Guicai;Song Xiaoxian;Zhang Haiting;Liang Ying;Dai Zijie;Yao Jianquan(School of Mechanical Engineering,Jiangsu University,Zhenjiang 212013,Jiangsu,China;College of Precision Instrument and Optoelectronic Engineering,Tianjin University,Tianjin 300072,China)
出处
《光学学报》
北大核心
2025年第2期283-290,共8页
Acta Optica Sinica
基金
国家自然科学基金(62205131)
江苏省自然科学基金青年项目(BK20220519,BK20240838)
红外物理国家重点实验室开放课题(SITP-NLIST-YB-2022-13)
江苏省高等学校基础科学(自然科学)研究项目(22KJB140002)
中国博士后科学基金项目(2022M721378,2023M741435)。
