To overcome the disadvantages of narrow frequency band and low transmittance for traditional nano-antenna, a nano-antenna structure based on cross-slots fractal was designed. The extraordinary optical transmission characteristics of the cross-slots fractal nano-antenna and the differences between the cross-slots fractal nano-antenna and the uniform cross-slots nano-antenna were analyzed by the finite difference time domain method. Meanwhile, the influence of physical parameters on the extraordinary optical transmission characteristics of the cross-slots fractal nano-antenna and the relationship of transmission spectrum of the nano-antenna between the fractal size and the non-fractal size were discussed. The results show that the fractal cross-slots structure is more miniaturized, and realizes extraordinary optical transmission and full 2π phase control of transmission beam, and the transmittance is higher than the uniform cross-slots structure, the full width at half maximum (FWHM) is wider, and the highest transmittance is up to 99.51%. By adjusting the physical parameters, the transmission spectrum exhibits red-shift or blue-shift characteristics, achieving controllability of the transmission spectrum. When h=50 nm, the full width at half maximum is about 356 nm, and the transmittance is still as high as 95.66%, which is generally higher than traditional structures, and the peak transmittance is still greater than 74% at large incident angles (70 degrees). In short, the cross-slots fractal nano-antenna has the characteristics of wide frequency, controllable and adjustable, and more miniaturized structure compared with other nano-antenna structures, and realizes extraordinary optical transmission.
Broadband cross-slots fractal nano-antenna and its extraordinary optical transmission characteristics
First published at:Jun 15, 2020
 Ebbesen T W, Lezec H J, Ghaemi H F, et al. Extraordinary optical transmission through sub-wavelength hole arrays[J]. Nature, 1998, 391(6668): 667–669.
 Bethe H A. Theory of diffraction by small holes[J]. Physical Review, 1944, 66(7–8): 163–182.
 He S L. The simulation and design of frequency selective surface with fractal pattern[D]. Wuhan: Huazhong University of Science & Technology, 2015.
何嵩磊. 基于分形图案的频率选择表面的仿真设计[D]. 武汉: 华中科技大学, 2015.
 Guo T. Review on plasmonic optical fiber grating biosensors[J]. Acta Optica Sinica, 2018, 38(3): 0328006.
郭团. 等离子体共振光纤光栅生物传感器综述[J]. 光学学报, 2018, 38(3): 0328006.
 Wang J L, Zhang B Z, Duan J P, et al. Flexible dual-stopband terahertz metamaterial filter[J]. Acta Optica Sinica, 2017, 37(10): 1016001.
王俊林, 张斌珍, 段俊萍, 等. 柔性双阻带太赫兹超材料滤波器[J]. 光学学报, 2017, 37(10): 1016001.
 Qi Y P, Zhang X W, Zhou P Y, et al. Refractive index sensor and filter of metal-insulator-metal waveguide based on ring resonator emb edded by cross structure[J]. Acta Physica Sinica, 2018, 67(19): 197301.
祁云平, 张雪伟, 周培阳, 等. 基于十字连通形环形谐振腔金属-介质-金属波导的折射率传感器和滤波器[J]. 物理学报, 2018, 67(19): 197301.
 Ghaemi H F, Thio T, Grupp D E, et al. Surface plasmons enhance optical transmission through subwavelength holes[J]. Physical Review B, 1998, 58(11): 6779–6782.
 Van Der Molen K L, Koerkamp K J K, Enoch S, et al. Role of shape and localized resonances in extraordinary transmission through periodic arrays of subwavelength holes: Experiment and theory[J]. Physical Review B, 2005, 72(4): 045421.
 Degiron A, Ebbesen T W. The role of localized surface plasmon modes in the enhanced transmission of periodic subwavelength apertures[J]. Journal of Optics A: Pure and Applied Optics, 2005, 7(2): S90–S96.
 Zhang X N, Liu G Q, Liu Z Q, et al. Near-field plasmon effects in extraordinary optical transmission through periodic triangular hole arrays[J]. Optical Engineering, 2014, 53(10): 107108.
 Zhang X N, Liu G Q, Liu Z Q, et al. Effects of compound rectangular subwavelength hole arrays on enhancing optical transmission[J]. IEEE Photonics Journal, 2015, 7(1): 4500408.
 Zhang W, Wang Y K, Luo L N, et al. Extraordinary optical transmission of broadband through tapered multilayer slits[J]. Plasmonics, 2015, 10(3): 547–551.
 Zhao B, Yang J J, Huang Z F. Anomalous transmission properties of two integrated metallic nanoslits under plasmonic cross talking coupling[J]. Acta Photonica Sinica, 2018, 47(3): 0324005.
赵波, 杨建军, 黄振芬. 基于表面等离激元交叉耦合作用的纳米金属双缝异常透射现象[J]. 光子学报, 2018, 47(3): 0324005.
 Xiao H. The research of multi-band and broadband antenna based on fractal structure[D]. Chengdu: University of Electronic Science and Technology of China, 2018.
肖花. 基于分形结构的多频与宽带天线研究[D]. 成都: 电子科技大学, 2018.
 De Nicola F, Purayil N S P, Spirito D, et al. Multiband plasmonic sierpinski carpet fractal antennas[J]. ACS Photonics, 2018, 5(6): 2418–2425.
 Puente-Baliarda C, Romeu J, Pous A, et al. On the behavior of the sierpinski multiband fractal antenna[J]. IEEE Transactions on Antennas and Propagation, 1998, 46(4): 517–524.
 Cakmakyapan S, Cinel N A, Cakmak A O, et al. Validation of electromagnetic field enhancement in near-infrared through sierpinski fractal nanoantennas[J]. Optics Express, 2014, 22(16): 19504–19512.
 Sivia J S, Kaur G, Sarao A K. A modified sierpinski carpet fractal antenna for multiband applications[J]. Wireless Personal Communications, 2017, 95(4): 4269–4279.
 Johnson P B, Christy R W. Optical constants of the noble metals[J]. Physical Review B, 1972, 6(12): 4370–4379.
Jiangxi Outstanding Youth Talent Funding Scheme (20171BCB23062), Jiangxi Natural Science Foundation (20171BAB204022), and Jiangxi Provincial Department of Education Science and Technology Research Key Project (GJJ170360)
Get Citation: Liu Juefu, Chen Jiao, Li Kangkang, et al. Broadband cross-slots fractal nano-antenna and its extraordinary optical transmission characteristics[J]. Opto-Electronic Engineering, 2020, 47(6): 190422.