基于领结型多孔光纤的双芯太赫兹偏振分束器
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摘要
领结型多孔光纤具有高双折射的特性,本文基于此设计了一种新型的双芯太赫兹(THz)偏振分束器,采用调整结构法实现了折射率反转匹配耦合,达到偏振分离.仿真结果表明:该偏振分束器在0.5—2.5 THz频率范围内均可实现偏振分离,最小分离长度仅为0.428 cm,且在整个频率范围内分离长度不超过2.5 cm.在2.3 THz,x,y两偏振模的吸收损耗均小于0.35 d B;消光比高达22.9和19.2 d B.此外,与填充法实现折射率反转匹配耦合的双芯THz偏振分束器进行比较,本文设计的偏振分束器实现简单,运行的频率范围更宽,分离长度更短,吸收损耗更低.
Terahertz(THz) radiation, which is defined as the electromagnetic wave with a frequency ranging from 0.1 THz to 10 THz, has attracted widespread attention in recent years because of its unique possibilities in many fields. Highperformance THz polarization splitter, a key device in THz manipulation, is of great significance for studying the THz devices. In the present paper, a novel dual-core THz polarization splitter is proposed, which is based on porous fiber with near-tie units. The introduction of near-tie units into the fiber core can enhance asymmetry to realize high mode birefringence. And the results show that the porous THz fiber exhibits high birefringence at a level of 10-2over a wide frequency range. An index converse matching coupling(ICMC) method, which exhibits several advantages(such as short splitting length, high extinction ratio, low loss, and broad operation bandwidth), is used to allow for the coupling of one polarization mode within a broad operation band, while the coupling of the other polarization component is effectively inhibited. The splitting length is equal to one coupling length of x- or y-polarization component for which inter-core coupling occurs, and short splitting length means low transmission loss. Unlike the reported filling method, an adjusting structure method is proposed in the paper to satisfy the condition of index converse matching coupling. The full vector finite element method(FEM), which is based on the variational principle and the subdivision interpolation, is used to analyze the guiding properties of the proposed THz polarization splitter. The FEM is a widely used numerical method in physical modeling and simulation. Simulation results show that the THz polarization splitter operates within a wide frequency range of 0.5–2.5 THz. The splitting length does not exceed 2.5 cm in the whole frequency range and the minimum is only 0.428 cm. At 2.3 THz, the material absorption losses of x- and y-polarization are both less than 0.35 d B, and the extinction ratios for x- and y-polarization are 2.9 and 19.2 d B, respectively. Moreover, by comparing with a THz polarization splitter with filling method, the proposed THz polarization with adjusting structure method is easier to realize, the operating frequency range is wider, the splitting length is shorter, and the material absorption loss is lower. Finally, we note that the fabrication of such THz porous fiber designs could be realized by several methods, such as a capillary stacking technique, a polymer casting technique, a hole drilling technique, etc.
Terahertz(THz) radiation, which is defined as the electromagnetic wave with a frequency ranging from 0.1 THz to 10 THz, has attracted widespread attention in recent years because of its unique possibilities in many fields. Highperformance THz polarization splitter, a key device in THz manipulation, is of great significance for studying the THz devices. In the present paper, a novel dual-core THz polarization splitter is proposed, which is based on porous fiber with near-tie units. The introduction of near-tie units into the fiber core can enhance asymmetry to realize high mode birefringence. And the results show that the porous THz fiber exhibits high birefringence at a level of 10-2over a wide frequency range. An index converse matching coupling(ICMC) method, which exhibits several advantages(such as short splitting length, high extinction ratio, low loss, and broad operation bandwidth), is used to allow for the coupling of one polarization mode within a broad operation band, while the coupling of the other polarization component is effectively inhibited. The splitting length is equal to one coupling length of x- or y-polarization component for which inter-core coupling occurs, and short splitting length means low transmission loss. Unlike the reported filling method, an adjusting structure method is proposed in the paper to satisfy the condition of index converse matching coupling. The full vector finite element method(FEM), which is based on the variational principle and the subdivision interpolation, is used to analyze the guiding properties of the proposed THz polarization splitter. The FEM is a widely used numerical method in physical modeling and simulation. Simulation results show that the THz polarization splitter operates within a wide frequency range of 0.5–2.5 THz. The splitting length does not exceed 2.5 cm in the whole frequency range and the minimum is only 0.428 cm. At 2.3 THz, the material absorption losses of x- and y-polarization are both less than 0.35 d B, and the extinction ratios for x- and y-polarization are 2.9 and 19.2 d B, respectively. Moreover, by comparing with a THz polarization splitter with filling method, the proposed THz polarization with adjusting structure method is easier to realize, the operating frequency range is wider, the splitting length is shorter, and the material absorption loss is lower. Finally, we note that the fabrication of such THz porous fiber designs could be realized by several methods, such as a capillary stacking technique, a polymer casting technique, a hole drilling technique, etc.
引文
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[5]Jiang H,Wang E,Zhang J,Hu L,Mao Q,Li Q 2014Opt.Express 22 30461
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[12]Zhu Y F 2014 Ph.D.Dissertation(Zhen Jiang:Jiangsu University)(in Chinese)[祝远锋2014博士学位论文(镇江:江苏大学)]
[13]Hou Y 2013 Ph.D.Dissertation(Tianjin:Nankai University)(in Chinese)[侯宇2013博士学位论文(天津:南开大学)]
[14]Wang C H 2013 Ph.D.Dissertation(Tianjin:Nankai University)(in Chinese)[王昌辉2013博士学位论文(天津:南开大学)]
[15]Wang J L,Yao J,Chen H,Zhong K,Li Z 2011 J.Opt.13 994
[16]Wang J L 2011 Ph.D.Dissertation(Tianjin:Tianjin University)(in Chinese)[汪静丽2011博士学位论文(天津:天津大学)]
[17]Ma J R 2007 M.S.Thesis(Hebei:Yanshan University)(in Chinese)[马景瑞2007硕士学位论文(河北:燕山大学)]
[2]Yong L,Han K,Lee B,Jung J 2003 Opt.Express 113359
[3]Florous N,Saitoh K,Koshiba M 2005 Opt.Express 137365
[4]Zhang S,Zhang W,Geng P,Li X,Ruan J 2011 Appl.Opt.50 6576
[5]Jiang H,Wang E,Zhang J,Hu L,Mao Q,Li Q 2014Opt.Express 22 30461
[6]Mao D,Guan C,Yuan L 2010 App.Opt.49 3748
[7]Saitoh K,Sato Y,Koshiba M 2004 Opt.Express 12 3940
[8]Wen K,Wang R,Wang J Y,Li J H 2008 Chinese Journal of Lasers 35 1962(in Chinese)[文科,王荣,汪井源,李建华2008中国激光35 1962]
[9]Bai J J,Wang C H,Hou Y,Fan F,Chang S J 2012 Acta Phys.Sin.61 108701(in Chinese)[白晋军,王昌辉,侯宇,范飞,常胜江2012物理学报61 108701]
[10]Jiang Z W,Bai J J,Hou Y,Bai X H,Chang S J 2013Acta Phys.Sin.62 028702(in Chinese)[姜子伟,白晋军,侯宇,王湘晖,常胜江2013物理学报62 028702]
[11]Li S S,Zhang H,Bai J,Liu W 2014 IEEE Photonics Technol.Lett.26 1399
[12]Zhu Y F 2014 Ph.D.Dissertation(Zhen Jiang:Jiangsu University)(in Chinese)[祝远锋2014博士学位论文(镇江:江苏大学)]
[13]Hou Y 2013 Ph.D.Dissertation(Tianjin:Nankai University)(in Chinese)[侯宇2013博士学位论文(天津:南开大学)]
[14]Wang C H 2013 Ph.D.Dissertation(Tianjin:Nankai University)(in Chinese)[王昌辉2013博士学位论文(天津:南开大学)]
[15]Wang J L,Yao J,Chen H,Zhong K,Li Z 2011 J.Opt.13 994
[16]Wang J L 2011 Ph.D.Dissertation(Tianjin:Tianjin University)(in Chinese)[汪静丽2011博士学位论文(天津:天津大学)]
[17]Ma J R 2007 M.S.Thesis(Hebei:Yanshan University)(in Chinese)[马景瑞2007硕士学位论文(河北:燕山大学)]