摘要:
提出了一种基于悬浮式双芯多孔光纤的低损耗、宽带太赫兹偏振分离器.通过纤芯的多孔结构实现器件的低损耗特性,利用两个纤芯微结构的正交关系实现宽带的单偏振模式匹配.结构参数设计采用折射率反转匹配耦合法；数值计算采用全矢量有限元法；光纤基底材料选择太赫兹波段低损耗环烯烃共聚物COC.首先对单芯高双折射悬浮式多孔光纤的色散、模式双折射、基模在空气中的能量分数、以及损耗等特性进行了分析,在此基础上,对悬浮式双芯多孔光纤偏振分离器的特性进行了详细研究.发现该偏振分离器的工作带宽超过1.5 THz (0.8 THz到2.3 THz).其偏振分离长度和吸收损耗随频率的增大而增大,在1 THz,分离长度仅为0.66 cm； x, y两偏振的消光比分别为-14.64 dB和-14.84 dB,两偏振模式的实际吸收损耗均小于0.12 dB.相对于其他双芯光纤偏振分离器设计,该结构具有宽带、低损耗、设计简单、拉制容易、以及抗环境干扰等优点.
Abstract:
A low loss broadband THz polarization splitter made from suspended dual-core porous fiber is proposed. The property of low loss is due to the porous structure of the fiber, and the match of single polarization mode is achieved by the orthogonal relationship of the microstructure in the two fiber cores. Structure of the fiber is designed by using index converse matching coupling method. Numerical simulation is carried out by employing full vector finite element method. The background material is cyclo olefin polymer COC with low loss property in THz region. Firstly, the properties of a suspended porous fiber with a single core has been analyzed in detail, including the effective refractive index, birefringence, fraction of modal power in air, and material absorption loss in the fundamental mode. Moreover, the properties of THz polarization splitter made from suspended dual-core porous fibers have been investigated theoretically. Numerical simulation results show that the operation bandwidth is 1.5 THz (from 0.8 THz to 2.3 THz). At 1 THz, the splitting length is only 0.66 cm. The extinction ratios for x and y polarization modes can reach -14.64 dB and-14.84 dB, respectively. The practical material absorption loss is less than 0.12 dB for both x and y polarization modes. Compared with other dual-core-PCF-based polarization splitters, the dual-core porous fiber has several advantages such as simplicity for structure designing, ease of fabrication, better feasibility in practical applications, low transmission loss, and wide operation frequency bandwidth.
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