摘要
连续域束缚态(BIC)已被广泛用于设计具有高品质因数(Q值)谐振的超材料中。通过在一个周期单元中设置两对高折射率裂环谐振器(SRR),设计了一种太赫兹全介质超材料。基于超晶格模式的对称性保护原理,通过改变其中两个SRR之间的距离,获得了可观测的准BIC(QBIC)模式。通过调节不对称度可以调制Q值,并且QBIC的Q值与结构的不对称度之间呈现出二次反比的关系。感应电场和磁场的空间分布以及感应电流的多极展开都表明了谐振是由电四极子的激发引起的。所提出的超材料具有较窄的谐振线宽,其灵敏度和FOM(figure of merit)分别为254.8 GHz/RIU和509.6,可以作为高灵敏度的折射率传感器。
Objective Bound state in the continuum(BIC)has been widely employed in designing metamaterials with high quality factor(Q-factor)resonances.BIC is a state that can still maintain localization in the continuum and can be explained by phase-canceling interference.When the system parameters are continuously adjusted,the coupling of the BIC resonance mode to all radiated waves disappears,which leads to an infinitely long lifetime and an infinitely high Q-factor.If the vanishing of the coupling constants is due to symmetry,the BIC is also called symmetry-protected BIC.Ideal BICs exist only in lossless and infinite structures,exhibiting infinite Q-factors and vanishing resonance linewidths,or transmission spectra with zero linewidths.In practice,the BIC can be changed to quasi-BIC by breaking the symmetry and generating a leakage resonance.Although the Q-factor and resonance linewidth will be limited at this point,the metamaterial can still have an ultra-high Q-factor with promising applications in sensors.Methods By setting up two pairs of split ring resonators(SRRs)with high refractive index in a periodic cell,we design a terahertz all-dielectric metamaterial(Fig.1).Based on the symmetry-preserving principle of superlattice modes,we obtain observable quasi-BIC(QBIC)modes by varying the distance between the two SRRs.Meanwhile,the variation rule of the Q-factor is obtained by calculating the energy distribution of the multipole to determine its resonance mode as shown in Fig.4 and by changing the different structural parameters as shown in Fig.6.Additionally,the transmission spectra with different background refractive indices are simulated to evaluate the sensing performance of the proposed metamaterial.Results and Discussions We simulate the transmission spectra of this all-dielectric SRR structure with different asymmetry parameters,and the Q-factor of QBIC decreases significantly under the increasing asymmetry parameter.The relationship between the Q-factor and the asymmetry parameter follows an inverse quadratic ratio.Fig.4(a)shows the multipole scattering energy distribution at a=0μm(BIC)and Fig.4(b)shows the multipole scattering energy distribution at a=12μm(QBIC).Near the resonant frequency of 0.6467 THz,the electric quadrupole increases significantly and dominates the far-field scattering energy distribution.Conclusions We design a terahertz sensor based on an all-dielectric metamaterial structure,with the Q-factor of the sensor as high as 2420.By simulating and analyzing the sensing performance of the designed metamaterial,the sensor achieves a sensitivity and an FOM of 254.8 GHz/RIU and 509.6 when the refractive index of the material to be measured varies from 1.00 to 1.04 respectively,and the sensor performance can be further improved by optimizing the structure.The sensor features a simple structure,low fabrication cost,and high sensitivity and FOM,and can be adopted as one with a high-sensitivity refractive index.
作者
岳帅
王豆豆
马天
田江锟
Yue Shuai;Wang Doudou;Ma Tian;Tian Jiangkun(College of Sciences,Xi'an University of Science and Technology,Xi'an 710054,Shaanxi,China;College of Safety Science and Engineering,Xi'an University of Science and Technology,Xi'an 710054,Shaanxi,China)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2023年第23期209-215,共7页
Acta Optica Sinica
基金
国家自然科学基金(11604260,12074309,52104218)
国家重点研发计划(2021YFE0105000)。
关键词
材料
连续域束缚态
太赫兹
全介质超材料
电四极子
折射率传感
materials
bound states in continuum
terahertz
all-dielectric metamaterial
electric quadrupole
refractive index sensing
