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A novel method is presented in this paper to realize terahertz even beam splitting by using a subwavelength binary simple periodic rectangular structure, for making comprehensive application of both the RCWA (Rigorous Couple-Wave Analysis) and the GA (Genetic Algorithm). By applying RCWA, the efficiency of each diffraction order can be numerically solved by using the structure parameters. To design an even beam splitter with a subwavelength structure is to find the optimal duty cycle f, period d, the grating depth h1 and the substrate thickness h2 to approach the minimum zero-order diffraction efficiency, the maximum sum of each non-zero-order diffraction efficiency, and the uniform distribution. Considering the three goals above, an evaluation function is established. GA is applied to optimize the evaluation function F, and then the optimal parameters of the splitter are obtained. When its period, groove depth, substrate thickness and duty ratio respectively equal to 269.7 μm, 175.2 μm, 18.1 μm and 0.409, the normal-incident TE-polarized terahertz plane wave with its frequency equal to 2.52 THz is divided evenly into the diffraction orders±1 and±2. It has a total efficiency up to 92.23% with a preferable result of reducing zero-order diffraction efficiency to 0.192% and an error of uniformity down to 6.51×10- 6, indicating an excellent performance of diffraction efficiency, uniformity and zero-order suppression as a terahertz even splitter. These results break the limitation of realizing even beam splitting in which the traditional scalar theory applies. In addition, this paper exposes the law of influence of the structure parameters, including ridge width, groove width, groove depth, duty ratio and substrate thickness, on the diffraction efficiency and its uniformity. It is found that only a small deviation of the structure parameters, corresponding to a deviation of ridge width a, groove width b, groove depth h1, and substrate thickness h2, less than 1 μm from the optimum design values, the element maintains good beam splitting performance. P0 is permitted to suppress to less than 2%, the error of uniformity U is better than 19.60%, and the diffraction efficiency maintains higher than 79.10%. With a substantial deviation from the design values of the structure parameters, the performance of the splitter will severely degrade and need to be redesigned.
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Keywords:
- subwavelength /
- binary rectangular periodic structure /
- terahertz even splitter /
- rigorous couple-wave
[1] Li J Z 2010 Handbook of Optics (Xi’an: Shanxi science and Technology Press of China) pp1070 (in Chinese) [李景镇 2010 光学手册(西安: 陕西科学技术出版社)第1070页]
[2] Philippe L, Jerome H, Pierre C, Edmond C, Huguette L 1999 J. Opt. A: Pure Appl. Opt. 1 215
[3] Zheng J J, Zhou C H, Feng J J, Cao H C, Lu P 2009 , Opt. Commun. 282 3069
[4] Wang B, Chen L, Lei L, Zhou J Y 2013 Optoelectron. Adv. Mat. 7 813
[5] Guan X W, Wu H, Shi Y C, Dai D X 2014 Opt. Lett. 39 259
[6] Wen F J, Chung P S 2011 Appl. Opt. 50 3187
[7] Wu J, Zhou C H, Cao H C, Hu A D, Yu J J, Sun W M, Jia W 2011 J. Opt. 13 115703
[8] Guo L W, Ma J Y 2014 Optik 125 232
[9] Hsu J H, Lee C H, Chen R S 2014 Microelectron. Eng. 113 74
[10] Feng J J, Zhou C H, Wang B, Zheng J J, Jia W, Cao H C, Lv P 2008 Appl. Opt. 47 6638
[11] Zhang J, Yan S H, Zhou C L, Shen S W, Li E, Tong H P 2008 Laser Journal 29 12 (in Chinese) [ 张军, 颜树华, 周春雷, 沈少伟, 李锷, 童慧鹏 2008 激光杂志 29 12]
[12] Huang H X, Ruan S C, Yang T, Xu P 2015 Nano-Micro Lett. 7 (in press)
[13] Xu P, Huang Y Y, Su Z J, Zhang X L, Luo T Z, Peng W D 2015 Opt. Express 23 4887
[14] Xu P, Zhang X L, Huang J F, Li B B, Ye E, Duan S F, Su Z J 2013 Opt. Express 21 20159
[15] Xu P, Huang H X, Wang K, Ruan S C, Yang J, Wan L L, Chen X X, Liu J Y 2007 Opt. Express 15 809
[16] Xu P, Huang Y Y, Su Z J, Zhang X L 2014 Appl. Opt. 53 1322
[17] Xu P, Hong C Q, Sun Z L, Han F, Cheng G X 2014 Opt. Commun. 315 97
[18] Xu P, Li J Z 2002 Science In China (Series E) 45 1
[19] Xu P, Zhou X, Zhang X C, Guo Y K, Guo L R, Tang H, Wu S D, Yang L X, Chen Y 1995 Opt. Rev. 2 362
[20] Huang H X, Xu P, Yang J, Gong X D, Wan L L, Wang K, Zheng Y Y, Han X 2009 Opt. Commun. 282 4198
[21] Xu P, Tan J Y, Guo L R, Guo Y K, Yang J F, Jiang N Y, Li Z, Du C L 1996 Acta Optica Sinica (Chinese) 16 1796
[22] Yan S H 2011 Design of diffraction microoptics (Beijing: National Defense Industry Press of China) chap. 12. (in Chinese) [ 颜树华, 2011 衍射微光学设计, (北京: 国防工业出版社)第 12 章]
[23] Marciante J R, Farmiga N O, Hirsh J I, Evans M S, Hieu T T 2003 Appl. Opt. 42 3234
[24] Moharam M G, Grann E B, Pommet D A, Gaylord T K 1995 J. Opt. Soc. Am. A 12 1068
[25] Cormier G, Boudreau R, Thériault S 2001 J. Opt. Soc. Am. B 18 1771
[26] Goldberg E 1987 Genetic Algorithm in Search, Optimization and Machine Learning(New York : Addison-Wesley Publishing Company).
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[1] Li J Z 2010 Handbook of Optics (Xi’an: Shanxi science and Technology Press of China) pp1070 (in Chinese) [李景镇 2010 光学手册(西安: 陕西科学技术出版社)第1070页]
[2] Philippe L, Jerome H, Pierre C, Edmond C, Huguette L 1999 J. Opt. A: Pure Appl. Opt. 1 215
[3] Zheng J J, Zhou C H, Feng J J, Cao H C, Lu P 2009 , Opt. Commun. 282 3069
[4] Wang B, Chen L, Lei L, Zhou J Y 2013 Optoelectron. Adv. Mat. 7 813
[5] Guan X W, Wu H, Shi Y C, Dai D X 2014 Opt. Lett. 39 259
[6] Wen F J, Chung P S 2011 Appl. Opt. 50 3187
[7] Wu J, Zhou C H, Cao H C, Hu A D, Yu J J, Sun W M, Jia W 2011 J. Opt. 13 115703
[8] Guo L W, Ma J Y 2014 Optik 125 232
[9] Hsu J H, Lee C H, Chen R S 2014 Microelectron. Eng. 113 74
[10] Feng J J, Zhou C H, Wang B, Zheng J J, Jia W, Cao H C, Lv P 2008 Appl. Opt. 47 6638
[11] Zhang J, Yan S H, Zhou C L, Shen S W, Li E, Tong H P 2008 Laser Journal 29 12 (in Chinese) [ 张军, 颜树华, 周春雷, 沈少伟, 李锷, 童慧鹏 2008 激光杂志 29 12]
[12] Huang H X, Ruan S C, Yang T, Xu P 2015 Nano-Micro Lett. 7 (in press)
[13] Xu P, Huang Y Y, Su Z J, Zhang X L, Luo T Z, Peng W D 2015 Opt. Express 23 4887
[14] Xu P, Zhang X L, Huang J F, Li B B, Ye E, Duan S F, Su Z J 2013 Opt. Express 21 20159
[15] Xu P, Huang H X, Wang K, Ruan S C, Yang J, Wan L L, Chen X X, Liu J Y 2007 Opt. Express 15 809
[16] Xu P, Huang Y Y, Su Z J, Zhang X L 2014 Appl. Opt. 53 1322
[17] Xu P, Hong C Q, Sun Z L, Han F, Cheng G X 2014 Opt. Commun. 315 97
[18] Xu P, Li J Z 2002 Science In China (Series E) 45 1
[19] Xu P, Zhou X, Zhang X C, Guo Y K, Guo L R, Tang H, Wu S D, Yang L X, Chen Y 1995 Opt. Rev. 2 362
[20] Huang H X, Xu P, Yang J, Gong X D, Wan L L, Wang K, Zheng Y Y, Han X 2009 Opt. Commun. 282 4198
[21] Xu P, Tan J Y, Guo L R, Guo Y K, Yang J F, Jiang N Y, Li Z, Du C L 1996 Acta Optica Sinica (Chinese) 16 1796
[22] Yan S H 2011 Design of diffraction microoptics (Beijing: National Defense Industry Press of China) chap. 12. (in Chinese) [ 颜树华, 2011 衍射微光学设计, (北京: 国防工业出版社)第 12 章]
[23] Marciante J R, Farmiga N O, Hirsh J I, Evans M S, Hieu T T 2003 Appl. Opt. 42 3234
[24] Moharam M G, Grann E B, Pommet D A, Gaylord T K 1995 J. Opt. Soc. Am. A 12 1068
[25] Cormier G, Boudreau R, Thériault S 2001 J. Opt. Soc. Am. B 18 1771
[26] Goldberg E 1987 Genetic Algorithm in Search, Optimization and Machine Learning(New York : Addison-Wesley Publishing Company).
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