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提出一种集成在微桥结构中的二维亚波长周期钛(Ti)金属圆盘阵列结构, 以增强太赫兹微测辐射热计的吸收率. 基于严格耦合波分析方法, 建立吸收结构模型, 研究了不同结构的Ti圆盘阵列及其在微桥阵列结构中的太赫兹波吸收特性. 周期Ti圆盘阵列结构降低了金属的表面等离子体频率, 在太赫兹波段激发伪表面等离子体激元并实现共振增强吸收. 共振吸收频率由周期、直径等Ti圆盘阵列的结构参数决定, 圆盘厚度则对太赫兹波吸收率有重要影响, 微桥结构中的谐振腔结构可降低共振频率并增强耦合效率. 设计的微桥探测结构以较小的Ti圆盘阵列周期(37 μm)实现突破衍射极限的太赫兹波约束, 在3.5 THz (波长85.7 μm)实现接近90%的太赫兹波吸收率, 满足太赫兹微测辐射热计小尺寸、高吸收及工艺兼容的要求.In this paper, a two-dimensional subwavelength periodic titanium (Ti) disk array integrated in micro-bridge structure is proposed to enhance the absorption of terahertz (THz) microbolometer. Based on the rigorous coupled wave analysis (RCWA) method, THz absorption characteristics of Ti disk arrays with different structure parameters in micro-bridge structure arrays are studied. Periodic disk array structure reduces the surface plasmon frequency of Ti, excites the spoof surface plasmons in the THz band and leads to resonance enhanced absorption. The resonance absorption frequency is determined by the structural parameters of Ti disk array including period and diameter while the absorption rate of THz wave is greatly affected by the thickness of Ti disks. The resonant cavity in micro-bridge structure can reduce the resonance frequency and enhance the coupling efficiency. The micro-bridge structure designed in this paper breaks the diffraction limit and traps the THz wave with a small period (37 μm). An absorption of nearly 90% is achieved at 3.5 THz. The structure meets the requirements of small size, high absorption and good process compatibility of the THz microbolometer.
[1] Qin B Y, Li Z, Hu F R, Hu C, Chen T, Zhang H, Zhao Y H 2018 IEEE Trans. Terahertz Sci. Technol. 8 149Google Scholar
[2] Peng Y, Qi B B, Jiang X K, Zhu Z, Zhao H W, Zhu Y M 2018 Appl. Phys. B 124 81Google Scholar
[3] Kanda N, Konishi K, Nemoto N, Midorikawa K, Kuwata-Gonokami M 2017 Sci. Rep. 7 42540Google Scholar
[4] Pan S, Du C H, Qi X B,Liu P K 2017 Sci. Rep. 7 7265Google Scholar
[5] Sirkeli V P, Yilmazoglu O, Preu S, FrankoKüppers, Hartnagel H L 2018 Sens. Lett. 16 1Google Scholar
[6] Hussin R, Liu L J, Luo Y 2017 IEEE Trans. Electron Devices 64 4450Google Scholar
[7] Li K, Hao Y, Jin X Q, Lu W 2018 J. Phys. D: Appl. Phys. 51 035104Google Scholar
[8] Uzawa Y, Kroug M, Kojima T, Makise K, Gonzalez A, Saito S, Fujii Y, Kaneko K, Terai H, Wang Z 2017 IEEE Trans. Appl. Supercond. 27 1500705Google Scholar
[9] Zhou T, Li H, Wan W J, Fu Z L, Cao J C 2017 AIP Adv. 7 105215Google Scholar
[10] Liang Z Q, Li S B, Liu Z J, Jiang Y D, Li W Z, Wang T, Wang J 2015 J. Mater. Sci.-Mater. Electron. 26 5400Google Scholar
[11] Nemoto N, Kanda N, Imai R, Konishi K, Miyoshi M, Kurashina S 2016 IEEE Trans. Terahertz Sci. Technol. 6 175Google Scholar
[12] Gou J, Niu Q C, Liang K, Wang J, Jiang Y D 2018 Nanoscale Res. Lett. 13 74Google Scholar
[13] Corcos D, Kaminski N, Shumaker E, Markish O, Elad D, Morf T, Drechsler U, Saha W T S, Kull L, Wood K, Pfeiffer U R, Grzyb J 2015 IEEE Trans. Terahertz Sci. Technol. 5 902Google Scholar
[14] Coppinger M J,Sustersic N A, Kolodzey J, Allik T H 2011 Opt. Eng. 50 053206Google Scholar
[15] Laman N, Grischkowsky D 2008 Appl. Phys. Lett. 93 051105Google Scholar
[16] Simoens F, Meilhan J 2014 Philos. Trans. R. Soc. A 372 20130111Google Scholar
[17] Gou J, WangJ, Zheng X, Gu D E, Yu H, Jiang Y D 2015 RSC Adv. 5 84252Google Scholar
[18] Gou J, Wang J, Li W Z, Tai H L, Gu D E, Jiang Y D 2013 J. Infrared, Millimeter, Terahertz Waves 34 431Google Scholar
[19] Alves F, Karamitros A, Grbovic D, Kearney B, Karunasiri G 2012 Opt. Eng. 51 063801Google Scholar
[20] Nguyen D T, Simoens F, Ouvrier-Buffet J L, Meilhan J, Coutaz J L 2012 IEEE Trans. Terahertz Sci. Technol. 2 299Google Scholar
[21] Oden J, Jérome M, Jérémy L D, Jean-François R, Frédéric G, Jean-Louis C, François S 2013 Opt. Express 21 4817Google Scholar
[22] Zhu P, Shi H, Guo L J 2012 Opt. Express 20 12521Google Scholar
[23] Pors A, Moreno E, Martin-Moreno L, Pendry J B, Garcia-Vidal F J 2012 Phys. Rev. Lett. 108 223905Google Scholar
[24] O'Hara J, Averitt R, Taylor A 2004 Opt. Express 12 6397Google Scholar
[25] Pendry J B, Martín-Moreno L, Garcia-Vidal F J 2004 Science 305 847Google Scholar
[26] Robertson K W, Lapierre R R, Krich J J 2019 Opt. Express 27 A133Google Scholar
[27] Weismann M, Gallagher D F G, Panoiu N C 2015 J. Opt. 17 125612Google Scholar
[28] Li L 1997 J. Opt. Soc. Am. A 14 2758Google Scholar
[29] Moharam M G, Gaylord T K 1983 J. Opt. Soc. Am. 73 1105Google Scholar
[30] Ordal M A, Bell R J, Alexander R W, Newquist L A, Querry M R 1988 Appl. Opt. 27 1203Google Scholar
[31] Cataldo G, Beall J A, Cho H M, Mcandrew B, Niemack M D, Wollack E J 2012 Opt. Lett. 37 4200Google Scholar
[32] Dragoman M, Dragoman D 2008 Prog. Quantum Electron. 32 1Google Scholar
[33] Ebbesen T W, Lezec H J, Ghaemi H F, Thio T, Wolff P A 1998 Nature 391 667Google Scholar
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图 1 吸收结构图 (a) 太赫兹微测辐射热计焦平面阵列的探测单元微桥结构; (b)二维亚波长Ti圆盘阵列俯视图; (c) 周期Ti圆盘阵列剖面图; (d) 增加反射层的吸收结构; (e) 增加反射层及支撑层的吸收结构; (f) 直角坐标系下的入射平面波与吸收结构模型
Fig. 1. Absorption structures: (a) Pixel structure of THz microbolometer focal plane array (FPA); (b) top view of a two-dimensional subwavelength Ti disk array; (c) sectional view of a periodic Ti disk array; (d) absorption structure with a reflection layer; (e) absorption structure with reflection layer and supporting layer; (f) absorption structure illuminated by a plane wave with a rectangular Cartesian coordinate system attached.
图 2 Ti与Si3N4的材料参数 (a) Ti在不同频率下的nTi与kTi值; (b) Si3N4在不同频率下的
${n_{{\rm{S}}{{\rm{i}}_3}{{\rm{N}}_4}}}$ 与$ {k_{{\rm{S}}{{\rm{i}}_3}{{\rm{N}}_4}}} $ 值Fig. 2. Material parameters of Ti and Si3N4: (a) nTi and kTi values of Ti at different frequencies; (b)
${n_{{\rm{S}}{{\rm{i}}_3}{{\rm{N}}_4}}}$ and$ {k_{{\rm{S}}{{\rm{i}}_3}{{\rm{N}}_4}}} $ values of Si3N4 at different frequencies.图 3 单层周期Ti圆盘阵列的太赫兹波吸收特性 (a)周期Ti圆盘阵列的太赫兹波反射率(R)、透射率(T)与吸收率(A)曲线(p = 37 μm, d = 14 μm, t = 10 nm), 插图为厚度10 nm的连续Ti薄膜的太赫兹波反射率(R)、透射率(T)与吸收率(A)曲线; (b)不同直径周期比(d/p)的Ti圆盘阵列在3.5 THz频率处的太赫兹波吸收率
Fig. 3. Terahertz wave absorption characteristics of single-layer periodic Ti disk array: (a) Terahertz wave reflection (R), transmission (T), and absorption (A) curves for periodic Ti disk arrays (p = 37 μm, d = 14 μm, t = 10 nm), inset: Reflection (R), transmission (T), and absorption (A) curves for a continuous Ti film with a thickness of 10 nm; (b) terahertz wave absorption at 3.5 THz for Ti disk arrays with different ratios of diameter and period (d/p).
图 4 带有真空腔、反射层与支撑层的Ti圆盘阵列的太赫兹波吸收特性 (a) 增加真空腔与反射层后连续Ti薄膜与Ti圆盘阵列(p = 37 μm, d = 28 μm)在不同频率下的太赫兹波反射率、透过率与吸收率; (b) 增加支撑层后连续Ti薄膜与不同直径(d)的Ti圆盘阵列(p = 37 μm)在不同频率下的太赫兹波吸收率
Fig. 4. Terahertz wave absorption characteristics of periodic Ti disk arrays with resonant cavity reflection layer and supporting layer: (a) Terahertz wave reflection (R), transmission (T) and absorption (A) curves for continuous Ti film and periodic Ti disk arrays with resonant cavity and reflection layer (p = 37 μm, d = 28 μm); (b) terahertz absorption curve for continuous Ti film and periodic Ti disk arrays with different diameters (d) and a supporting layer (p = 37 μm).
图 5 不同Si3N4支撑层厚度与Ti圆盘厚度的吸收结构的太赫兹波吸收特性 (a)不同Si3N4支撑层厚度(h)的吸收结构在不同频率下的太赫兹波吸收率(p = 37 μm, d = 34 μm, t = 10 nm); (b)不同Ti圆盘厚度(t)的吸收结构在不同频率下的太赫兹波吸收率, 插图为不同Ti圆盘厚度(t)的吸收结构在3.5 THz下的峰值吸收率(p = 37 μm, d = 34 μm)
Fig. 5. Terahertz wave absorption characteristics of periodic Ti disk arrays with different thicknesses of supporting layer and Ti disks: (a) Terahertz absorption at different frequencies for absorption structures with different thicknesses (h) of Si3N4 support layers (p = 37 μm, d = 34 μm, t = 10 nm); (b) terahertz absorption at different frequencies for absorption structures with different thicknesses (t) of Ti disks; Inset: Peak absorption rate at 3.5 THz for absorbing structures with different thicknesses (t) of Ti disks (p = 37 μm, d = 34 μm).
图 6 共振吸收频率(3.5 THz)下吸收结构的电场分布 (a) yz平面上吸收结构的电场分布; (b) xy平面上吸收结构的电场分布(p = 37 μm, d = 34 μm, t = 40 nm)
Fig. 6. Electric field distribution of the absorption structure at the resonance absorption frequency (3.5 THz): (a) Electric field distribution in the yz plane; (b) electric field distribution in the xy plane (p = 37 μm, d = 34 μm, t = 40 nm).
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[1] Qin B Y, Li Z, Hu F R, Hu C, Chen T, Zhang H, Zhao Y H 2018 IEEE Trans. Terahertz Sci. Technol. 8 149Google Scholar
[2] Peng Y, Qi B B, Jiang X K, Zhu Z, Zhao H W, Zhu Y M 2018 Appl. Phys. B 124 81Google Scholar
[3] Kanda N, Konishi K, Nemoto N, Midorikawa K, Kuwata-Gonokami M 2017 Sci. Rep. 7 42540Google Scholar
[4] Pan S, Du C H, Qi X B,Liu P K 2017 Sci. Rep. 7 7265Google Scholar
[5] Sirkeli V P, Yilmazoglu O, Preu S, FrankoKüppers, Hartnagel H L 2018 Sens. Lett. 16 1Google Scholar
[6] Hussin R, Liu L J, Luo Y 2017 IEEE Trans. Electron Devices 64 4450Google Scholar
[7] Li K, Hao Y, Jin X Q, Lu W 2018 J. Phys. D: Appl. Phys. 51 035104Google Scholar
[8] Uzawa Y, Kroug M, Kojima T, Makise K, Gonzalez A, Saito S, Fujii Y, Kaneko K, Terai H, Wang Z 2017 IEEE Trans. Appl. Supercond. 27 1500705Google Scholar
[9] Zhou T, Li H, Wan W J, Fu Z L, Cao J C 2017 AIP Adv. 7 105215Google Scholar
[10] Liang Z Q, Li S B, Liu Z J, Jiang Y D, Li W Z, Wang T, Wang J 2015 J. Mater. Sci.-Mater. Electron. 26 5400Google Scholar
[11] Nemoto N, Kanda N, Imai R, Konishi K, Miyoshi M, Kurashina S 2016 IEEE Trans. Terahertz Sci. Technol. 6 175Google Scholar
[12] Gou J, Niu Q C, Liang K, Wang J, Jiang Y D 2018 Nanoscale Res. Lett. 13 74Google Scholar
[13] Corcos D, Kaminski N, Shumaker E, Markish O, Elad D, Morf T, Drechsler U, Saha W T S, Kull L, Wood K, Pfeiffer U R, Grzyb J 2015 IEEE Trans. Terahertz Sci. Technol. 5 902Google Scholar
[14] Coppinger M J,Sustersic N A, Kolodzey J, Allik T H 2011 Opt. Eng. 50 053206Google Scholar
[15] Laman N, Grischkowsky D 2008 Appl. Phys. Lett. 93 051105Google Scholar
[16] Simoens F, Meilhan J 2014 Philos. Trans. R. Soc. A 372 20130111Google Scholar
[17] Gou J, WangJ, Zheng X, Gu D E, Yu H, Jiang Y D 2015 RSC Adv. 5 84252Google Scholar
[18] Gou J, Wang J, Li W Z, Tai H L, Gu D E, Jiang Y D 2013 J. Infrared, Millimeter, Terahertz Waves 34 431Google Scholar
[19] Alves F, Karamitros A, Grbovic D, Kearney B, Karunasiri G 2012 Opt. Eng. 51 063801Google Scholar
[20] Nguyen D T, Simoens F, Ouvrier-Buffet J L, Meilhan J, Coutaz J L 2012 IEEE Trans. Terahertz Sci. Technol. 2 299Google Scholar
[21] Oden J, Jérome M, Jérémy L D, Jean-François R, Frédéric G, Jean-Louis C, François S 2013 Opt. Express 21 4817Google Scholar
[22] Zhu P, Shi H, Guo L J 2012 Opt. Express 20 12521Google Scholar
[23] Pors A, Moreno E, Martin-Moreno L, Pendry J B, Garcia-Vidal F J 2012 Phys. Rev. Lett. 108 223905Google Scholar
[24] O'Hara J, Averitt R, Taylor A 2004 Opt. Express 12 6397Google Scholar
[25] Pendry J B, Martín-Moreno L, Garcia-Vidal F J 2004 Science 305 847Google Scholar
[26] Robertson K W, Lapierre R R, Krich J J 2019 Opt. Express 27 A133Google Scholar
[27] Weismann M, Gallagher D F G, Panoiu N C 2015 J. Opt. 17 125612Google Scholar
[28] Li L 1997 J. Opt. Soc. Am. A 14 2758Google Scholar
[29] Moharam M G, Gaylord T K 1983 J. Opt. Soc. Am. 73 1105Google Scholar
[30] Ordal M A, Bell R J, Alexander R W, Newquist L A, Querry M R 1988 Appl. Opt. 27 1203Google Scholar
[31] Cataldo G, Beall J A, Cho H M, Mcandrew B, Niemack M D, Wollack E J 2012 Opt. Lett. 37 4200Google Scholar
[32] Dragoman M, Dragoman D 2008 Prog. Quantum Electron. 32 1Google Scholar
[33] Ebbesen T W, Lezec H J, Ghaemi H F, Thio T, Wolff P A 1998 Nature 391 667Google Scholar
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