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Terahertz metamaterial (THz MM) absorber, as an important type of MM functional device, can not only achieve perfect absorption of incident THz waves, but also act as a refractive index sensor to capture and monitor changes in the information about surrounding environment. Generally, the sensing characteristics of the THz MM absorber can be improved by optimizing the structure of the surface metal resonance unit and changing the material and shape of the dielectric layer. In order to further study the influence of the intermediate dielectric layer on the sensing characteristics of the THz MM absorber, in this paper we implement three THz MM absorbers with continuous dielectric layer, discontinuous dielectric layer and microcavity structure based on the metallic split-ring resonator array, and conduct in-depth study of their sensing characteristics and sensing mechanism. The THz MM absorber with continuous dielectric layer and metallic split-ring resonator array can be used as a refractive index sensor to realize the sensing detection of analytes coated on its surface with different refractive indexes. However, it can be seen from its corresponding refractive index frequency sensitivity and FOM value that the detection sensitivity of this sensor is limited, and its sensing performance still needs improving. The main reason is that most of the resonant electromagnetic (EM) field of the THz MM absorber is tightly bound in the intermediate dielectric layer, and only the fringe field extending to the surface of the MM absorber resonant unit array can interact with the analyte to be measured, and the intensity of this part of the field directly determines the sensitivity of the sensor. In order to further improve the refractive index frequency sensitivity of the THz MM absorber, reduce the restriction of the intermediate dielectric layer to the resonant EM field, and enhance the interaction between the resonant EM field and the analyte to be measured, a THz MM absorber with discontinuous dielectric layer is proposed and studied. Compared with the THz MM absorber with continuous dielectric layer, the THz MM absorber based on discontinuous dielectric layer can be used as a refractive index sensor to realize higher-sensitivity sensing and detection of the analyte coated on the surface. In order to further enhance the interaction between the resonant EM field and the analyte to be measured, and improve the refractive index frequency sensitivity of the THz MM absorber, a THz MM absorber with a microcavity structure is proposed. For this THz MM absorber, the analyte to be measured filled in the microcavity structure can serve as the intermediate dielectric layer of the THz MM absorber, and when the metallic split-ring resonator array is completely immersed in the analyte to be measured, the resonant EM field originally confined in the intermediate dielectric layer and the analyte to be measured completely overlap in space. Therefore, compared with the first two THz MM absorbers, THz MM absorber with a microcavity structure achieves the tightly and fully contacting the resonant EM field, thereby greatly improving its sensitivity as a sensor. The results show that in order to improve the sensing characteristics of the THz MM absorber, such as the refractive index sensitivity and the maximum detection range, in addition to using the materials with lower relatively permittivity as the intermediate dielectric layer, the morphology of the intermediate dielectric layer can be changed, thereby reducing the restraint of the intermediate dielectric layer on the resonant field and enhancing the coupling between the resonant field and the analyte to be measured. Compared with the conventional THz MM absorber with continuous dielectric layer, the MM absorber with discontinuous dielectric layer and microcavity structure have many superior sensing characteristics, and can be applied to the high-sensitivity and rapid detection of analytes to be measured, and has a broader application prospect in the future sensing field. -
Keywords:
- terahertz /
- metamaterial absorber /
- sensing
[1] Lee Y K 2012 太赫兹科学与技术原理 (北京: 国防工业出版社) 第1−30页
Lee Y K 2012 Principles of Terahertz Science and Technology (Beijing: National Defense Industry Press) pp1−30 (in Chinese)
[2] Zhang X C, Alexander S, Zhang Y 2017 Nat. Photonics 11 16
Google Scholar
[3] Zhang X C, Xu J Z 2010 Introduction to THz Wave Photonics (New York: Springer US) pp1−26
[4] 张活 2018 博士学位论文 (西安: 西安电子科技大学)
Zhang H 2018 Ph. D. Dissertation (Xi’an: Xidian University) (in Chinese)
[5] Wang J, Wang S, Singh R 2013 Chin. Opt. Lett. 11 011602
Google Scholar
[6] Wang X, Zhang B Z, Wang W J, Wang J L, Duan J P 2017 IEEE Photonics J. 9 4600512
Google Scholar
[7] 黄文媛 2013 硕士学位论文 (成都: 西南交通大学)
Huang W Y 2013 M. S. Dissertation (Chengdu: Southwest Jiaotong University) (in Chinese)
[8] Li S Y, Ai X C, Wu R H 2018 Opt. Commun. 428 251
Google Scholar
[9] 闫昕, 张兴坊, 梁兰菊, 姚建铨 2014 光谱学与光谱分析 2365
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Yan X, Zhang X F, Liang L J, Yao J Q 2014 Spectrosc. Spect. Anal. 2365
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Zhang Y P, Li T T, Lv H H 2015 Acta Phys. Sin. 64 117801
Google Scholar
[12] Wang X, Zhang B Z, Wang W J, Duan J P 2017 IEEE Photonics J. 9 4600213
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[13] 毛前军, 冯春早 2019 光学学报 39 0816001
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Mao Q J, Feng C Z 2019 Acta Opt. Sin. 39 0816001
Google Scholar
[14] Wang W, Yan F P, Tan S Y 2017 Photonics Res. 5 571
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[15] Yan X, Yang M S, Zhang Z 2019 Biosens. Bioelectron. 126 485
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[16] Srivastava Y K, Cong L Q, Singh R 2017 Appl. Phys. Lett. 111 201101
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[17] Ahmed S, Sungjoon L 2018 Biosens. Bioelectron. 117 398
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[18] Han B J, Han Z H, Qin J Y 2019 Talanta 192 1
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[19] Singh R, Al-Naib A I, Koch M 2010 Opt. Express 18 13044
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[20] Saraswati B, Kyoungsik K 2019 J. Phys. D: Appl. Phys. 52 275106
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[21] Li W Y, Su Y, Zhai X 2018 IEEE Photonic. Tech. Lett. 30 2068
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[22] Shen S M, Liu Y L, Liu W Q 2018 Mater. Res. Express 5 125804
Google Scholar
[23] Hu T, Strikwerda A C, Liu M 2010 Appl. Phys. Lett. 97 261909
Google Scholar
[24] Moritake Y, Tanaka T 2018 Opt. Express 26 3674
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[26] Wang W, Yan F P, Tan S Y 2020 Photonics Res. 8 519
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[34] Wang B X, Zhai X, Wang G Z 2015 Appl. Phys. 117 014504
Google Scholar
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图 1 基于连续介质层和金属开口谐振环阵列的太赫兹超材料吸波器的结构示意图
Figure 1. Schematic diagram of THz MM absorber based on continuous dielectric layer and metallic split-ring resonator array.
图 2 具有连续介质层的太赫兹超材料吸波器的吸收特性仿真曲线
Figure 2. Simulated absorption characteristic curve of THz MM absorber with continuous dielectric layer.
图 3 (a) 谐振频率处的表面电流分布; (b) 谐振频率处的表面电场分布
Figure 3. (a) Surface current distribution at the resonance frequency; (b) surface electric field distribution at the resonance frequency.
图 4 (a) 谐振频率处
$y$ = 0 截面的电场分布; (b) 谐振频率处$x$ = 0 截面的磁场分布Figure 4. (a) Electric field distribution at cross section of
$y$ = 0 at the resonance frequency; (b) magnetic field distribution at cross section of$x$ = 0 at the resonance frequency
图 5 在分析物折射率从n = 1变化到n = 1.8时具有连续介质层的太赫兹超材料吸波器的吸收特性仿真曲线
Figure 5. Simulated absorption characteristic curves of THz MM absorber with continuous dielectric layer under analyte refractive index changes from n = 1 to n = 1.8.
图 6 在分析物折射率从n = 1变化到n = 1.8时具有连续介质层的太赫兹超材料吸波器的谐振频率偏移及其线性拟合
Figure 6. Resonance frequency shifts and linear fitting of THz MM absorber with continuous dielectric layer under analyte refractive index changes from n = 1 to n = 1.8.
图 7 介质层材料的相对介电常数变化对传感器折射率频率灵敏度的影响
Figure 7. Influence of relative permittivity of dielectric layer material on the refractive index frequency sensitivity of the sensor.
图 8 在分析物厚度不同条件下, 分析物折射率从n = 1变化到n = 1.8时具有连续介质层的太赫兹超材料吸波器的谐振频率偏移
Figure 8. Resonance frequency shifts of THz MM absorber with continuous dielectric layer under analyte refractive index changes from n = 1 to n = 1.8 for different thicknesses of the analyte.
图 9 选用连续介质层的太赫兹超材料吸波器作为传感器时, 被测分析物厚度对传感器折射率频率灵敏度的影响
Figure 9. Influence of the thickness of the analyte to be measured on the refractive index frequency sensitivity of the sensor for the THz MM absorber with continuous dielectric layer.
图 10 基于非连续介质层和金属开口谐振环阵列的太赫兹超材料吸波器的结构示意图
Figure 10. Schematic diagram of THz MM absorber based on discontinuous dielectric layer and metallic split-ring resonator array.
图 11 具有非连续介质层的太赫兹超材料吸波器的吸收特性仿真曲线
Figure 11. Simulated absorption characteristic curve of THz MM absorber with discontinuous dielectric layer.
图 12 在分析物折射率从n = 1变化到n = 1.8时具有非连续介质层的太赫兹超材料吸波器的吸收特性仿真曲线
Figure 12. Simulated absorption characteristic curves of THz MM absorber with discontinuous dielectric layer under analyte refractive index changes from n = 1 to n = 1.8.
图 13 在分析物折射率从n = 1变化到n = 1.8时具有非连续介质层的太赫兹超材料吸波器的谐振频率偏移及其线性拟合
Figure 13. Resonance frequency shifts and linear fitting of THz MM absorber with discontinuous dielectric layer under analyte refractive index changes from n = 1 to n = 1.8.
图 14 在分析物厚度不同条件下, 分析物折射率从n = 1变化到n = 1.8时具有非连续介质层的太赫兹超材料吸波器的谐振频率偏移
Figure 14. Resonance frequency shifts of THz MM absorber with discontinuous dielectric layer under analyte refractive index changes from n = 1 to n = 1.8 for different thicknesses of the analyte.
图 15 选用非连续介质层的太赫兹超材料吸波器作为传感器时, 被测分析物厚度对传感器折射率频率灵敏度的影响
Figure 15. Influence of the thickness of the analyte to be measured on the refractive index frequency sensitivity of the sensor for the THz MM absorber with discontinuous dielectric layer.
图 16 待测分析物充当介质层的太赫兹超材料吸波器的结构示意图
Figure 16. Schematic diagram of THz MM absorber whose analyte to be measured acts as dielectric layer.
图 17 未填充待测分析物的太赫兹超材料吸波器的吸收特性仿真曲线
Figure 17. Simulated absorption characteristic curve of THz MM absorber without filling the analyte to be measured.
图 18 分析物折射率从n = 1变化到n=1.8时具有微腔结构的太赫兹超材料吸波器的吸收特性仿真曲线
Figure 18. Simulated absorption characteristic curve of THz MM absorber with microcavity structure under analyte refractive index range from n = 1 to n = 1.8.
图 19 分析物折射率从n = 1变化到n = 1.8时具有微腔结构的太赫兹超材料吸波器的谐振频率偏移及其线性拟合
Figure 19. Resonance frequency shifts and linear fitting of THz MM absorber with microcavity structure under analyte refractive index changes from n = 1 to n = 1.8.
表 1 太赫兹超材料吸波器的参数对比
Table 1. Comparison of parameters of THz MM absorbers
太赫兹超材料吸波器的
吸收与传感特性参数具有不同介质层的太赫兹超材料吸波器 连续介质层 非连续介质层 微腔结构 谐振频率/THz 0.183 0.245 0.277 吸收率/% 99.97 93.30 86.60 谐振峰半高宽FWHM/GHz 9.3 13.0 15.0 品质因数Q 19.7 18.8 18.4 折射率灵敏度S/(GHz·RIU–1) 8.6 65.8 101.5 FOM值 0.92 5.06 6.77 
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[1] Lee Y K 2012 太赫兹科学与技术原理 (北京: 国防工业出版社) 第1−30页
Lee Y K 2012 Principles of Terahertz Science and Technology (Beijing: National Defense Industry Press) pp1−30 (in Chinese)
[2] Zhang X C, Alexander S, Zhang Y 2017 Nat. Photonics 11 16
Google Scholar
[3] Zhang X C, Xu J Z 2010 Introduction to THz Wave Photonics (New York: Springer US) pp1−26
[4] 张活 2018 博士学位论文 (西安: 西安电子科技大学)
Zhang H 2018 Ph. D. Dissertation (Xi’an: Xidian University) (in Chinese)
[5] Wang J, Wang S, Singh R 2013 Chin. Opt. Lett. 11 011602
Google Scholar
[6] Wang X, Zhang B Z, Wang W J, Wang J L, Duan J P 2017 IEEE Photonics J. 9 4600512
Google Scholar
[7] 黄文媛 2013 硕士学位论文 (成都: 西南交通大学)
Huang W Y 2013 M. S. Dissertation (Chengdu: Southwest Jiaotong University) (in Chinese)
[8] Li S Y, Ai X C, Wu R H 2018 Opt. Commun. 428 251
Google Scholar
[9] 闫昕, 张兴坊, 梁兰菊, 姚建铨 2014 光谱学与光谱分析 2365
Google Scholar
Yan X, Zhang X F, Liang L J, Yao J Q 2014 Spectrosc. Spect. Anal. 2365
Google Scholar
[10] Chen T, Li S, Sun H 2012 Sensors 12 2742
Google Scholar
[11] 张玉萍, 李彤彤, 吕欢欢 2015 物理学报 64 117801
Google Scholar
Zhang Y P, Li T T, Lv H H 2015 Acta Phys. Sin. 64 117801
Google Scholar
[12] Wang X, Zhang B Z, Wang W J, Duan J P 2017 IEEE Photonics J. 9 4600213
Google Scholar
[13] 毛前军, 冯春早 2019 光学学报 39 0816001
Google Scholar
Mao Q J, Feng C Z 2019 Acta Opt. Sin. 39 0816001
Google Scholar
[14] Wang W, Yan F P, Tan S Y 2017 Photonics Res. 5 571
Google Scholar
[15] Yan X, Yang M S, Zhang Z 2019 Biosens. Bioelectron. 126 485
Google Scholar
[16] Srivastava Y K, Cong L Q, Singh R 2017 Appl. Phys. Lett. 111 201101
Google Scholar
[17] Ahmed S, Sungjoon L 2018 Biosens. Bioelectron. 117 398
Google Scholar
[18] Han B J, Han Z H, Qin J Y 2019 Talanta 192 1
Google Scholar
[19] Singh R, Al-Naib A I, Koch M 2010 Opt. Express 18 13044
Google Scholar
[20] Saraswati B, Kyoungsik K 2019 J. Phys. D: Appl. Phys. 52 275106
Google Scholar
[21] Li W Y, Su Y, Zhai X 2018 IEEE Photonic. Tech. Lett. 30 2068
Google Scholar
[22] Shen S M, Liu Y L, Liu W Q 2018 Mater. Res. Express 5 125804
Google Scholar
[23] Hu T, Strikwerda A C, Liu M 2010 Appl. Phys. Lett. 97 261909
Google Scholar
[24] Moritake Y, Tanaka T 2018 Opt. Express 26 3674
Google Scholar
[25] Brian B, Sepúlveda B, Alaverdyan Y, Lechuga L M, Käll M 2009 Opt. Express 17 2015
Google Scholar
[26] Wang W, Yan F P, Tan S Y 2020 Photonics Res. 8 519
Google Scholar
[27] Meng K, Park S J, Burnett A D 2019 Opt. Express 27 23164
Google Scholar
[28] Hu T, Chieffo L R, Brenckle M A, et al. 2016 Adv. Mater. 23 3197
Google Scholar
[29] Dmitriev A, Hägglund C, Chen S 2008 Nano Lett. 8 3893
Google Scholar
[30] Whitesides G M 2006 Nature 442 368
Google Scholar
[31] Zhou H, Hu D L, Yang C 2018 Sci. Rep. 8 14801
Google Scholar
[32] Hu X, Xu G Q, Wen L 2016 Laser Photonics Rev. 10 962
Google Scholar
[33] Janneh M, De Marcellis A, Palange E 2018 Opt. Commun. 416 152
Google Scholar
[34] Wang B X, Zhai X, Wang G Z 2015 Appl. Phys. 117 014504
Google Scholar
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