1.School of Mechanical and Engineering, Jiangsu University, Zhenjiang 212013, China 2.Institute of Micro-nano Optoelectronics and Terahertz Technology, Jiangsu University, Zhenjiang 212013, China 3.College of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
Fund Project:Project supported by the China Postdoctoral Science Foundation (Grant No. 2019M651725), the Natural Science Foundation of Jiangsu Province, China (Grant Nos. BK20180862, BK20190839), and the Graduate Research Innovation Project of Jiangsu Province, China (Grant No. KYCX19_1583)
Received Date:10 August 2019
Accepted Date:16 September 2019
Available Online:27 November 2019
Published Online:01 December 2019
Abstract:With the increasing scarcity of spectrum resources, terahertz wave technologies have attracted more and more attention in recent decades, and have made tremendous progress. Terahertz wave referring to electromagnetic waves with a frequency in a range of 0.1-10 THz has a wide range of applications in wireless communication, nondestructive imaging and remote sensing. Due to the advantages of high absorption, ultra-thin thickness, frequency selectivity and design flexibility, metamaterial absorbers have attracted more attention in terahertz band. In this paper, two terahertz metamaterial absorbers with different performances are designed which are named “T” terahertz multi-band absorber and “T” terahertz tunable broadband absorber, respectively. The absorbers are both comprised of three layers: metal substrate, matched dielectric layer and surface metamaterial layer. The main structures of these two absorbers are composed of four T-shape Au plates on the top of polyimide dielectric layer and an Au sheet acting as a bottom layer. The only difference between these two absorbers is that the terahertz broadband tunable absorber possesses a square photosensitive silicon in the metamaterial layer. The simulations results show that the terahertz multi-band absorber has six absorption peaks at 2.918, 3.7925, 4.986, 6.966, 7.2685, and 7.4665 THz, with the absorptivity peaks of 95.631%, 99.508%, 96.34%, 94.835%, 96.485%, 94.732%, respectively, and the average absorption rate is 96.26%. Terahertz tunable broadband absorber has the characteristics of broadband absorption. When the conductivity of silicon is 1600 S/m, the absorber reaches its absorption peak at 0.786 THz with the absorptivity of 99.998%, and the frequency bandwidth with the absorption rate exceeding 90% reaches 240 GHz. The more interesting thing is that by changing the conductivity of silicon, the terahertz tunable broadband absorber shows the ability to dynamically control the existence of absorption band and adjust the frequency position of absorption peak. For terahertz tunable broadband absorber, the frequency of absorption peak can be regulated in a bandwidth of about 30 GHz. The terahertz wave absorbers designed in this paper possess rather simple structures, therefore the proposed absorbers are easy to fabricate. Because of these excellent properties, the absorbers may have potential applications in optical switch, optical detection, optical imaging, band-stop devices, and other fields. Keywords:terahertz absorber/ multi-band absorber/ tunable broadband/ metamaterial
图 4 硅电导率在1—1000 S/m范围内六种不同取值下的太赫兹波吸收器吸收谱 Figure4. Absorption spectra of terahertz absorbers with six different values of silicon conductivity in the range of 1?1000 S/m.
图 5 硅电导率为1600 S/m时的超材料太赫兹波吸收器吸收谱 Figure5. Absorption spectra of metamaterial terahertz absorbers when silicon conductivity is 1600 S/m.
图 6 硅电导率在1000?4000 S/m范围内六种不同取值下的太赫兹波吸收器吸收谱 Figure6. Absorption spectra of terahertz absorbers with six different values of silicon conductivity in the range of 1000?4000 S/m.
24.3.仿真结果分析 -->
4.3.仿真结果分析
为了进一步地说明“T”型图案太赫兹超材料多频吸收器以及宽频可调谐吸收器的吸收机理, 分别研究了多频吸收器在各个吸收峰频率的磁场分布, 以及宽频可调谐吸收器在硅电导率为1600 S/m时0.78 THz频率点的上下表面的表面电流分布情况, 结果如图7和图8所示. 图 7 多频吸收器超材料结构层在2.918 THz处的磁场分布情况 Figure7. Distribution of magnetic field at 2.918 THz in metamaterial structure layer of terahertz multi-band absorber.
图 8 宽频可调谐吸收器在硅电导率为1600 S/m时0.78 THz频率点的上下表面的表面电流分布情况 (a)上表面; (b)下表面 Figure8. Terahertz tunable broadband absorber of surface current distribution on upper and lower surfaces at 0.78 THz when silicon conductivity is 1600 S/m: (a) Upper surface; (b) lower surface.