Wang Dawei, Hu Yujie, Yue Wencheng, Zeng Youhong, Tu Zhijuan, Cai Yan, Wang Wei, Fang Qing, Yu Mingbin
Appl Opt. 2019 Oct 20;58(30):8221-8226. doi: 10.1364/AO.58.008221.
In this paper, a novel, to the best of our knowledge, polarization beam splitter (PBS) based on an asymmetrical directional coupler (DC) was proposed, which consists of a strip waveguide (WG) and a ${{\rm Si}_3}{{\rm N}_4}$SiN loaded horizontal slot WG. By carefully adjusting the geometric parameters of the DC, the phase match condition between these two WGs can be satisfied for the transverse magnetic (TM) polarization, while the coupling efficiency of the transverse electric (TE) polarization is frustrated due to the large phase mismatch. The extra optimizing designs include adding filters to the output ports as well as introducing the tapered structure into the DC, which is settled by the particle swarm optimizing (PSO) algorithm so that the performance of the proposed PBS is improved over a broadband range. Numerical simulations show that the bandwidths for the extinction ratio (ER) $ \gt {20};{\rm dB}$>20dB, 30 dB, and 40 dB are 160 nm, 95 nm, and 50 nm, respectively, with insertion loss (IL) $ \lt {1};{\rm dB}$<1dB for the wavelength of 1.49-1.58 µm. The analysis of the deviations demonstrates that the proposed PBS allows high fabrication tolerances.
在本文中，据我们所知，提出了一种基于非对称定向耦合器（DC）的新型偏振分束器（PBS），它由一个条形波导（WG）和一个负载有${{\rm Si}_3}{{\rm N}_4}$的水平槽形波导组成。通过仔细调整定向耦合器的几何参数，可以使这两个波导之间满足横向磁（TM）偏振的相位匹配条件，而横向电（TE）偏振的耦合效率由于较大的相位失配而受到抑制。额外的优化设计包括在输出端口添加滤波器以及在定向耦合器中引入渐变结构，这是通过粒子群优化（PSO）算法实现的，从而使所提出的偏振分束器在宽带范围内的性能得到改善。数值模拟表明，对于波长为1.49 - 1.58 µm，消光比（ER）>20 dB、30 dB和40 dB时的带宽分别为160 nm、95 nm和50 nm，插入损耗（IL）<1 dB。偏差分析表明，所提出的偏振分束器具有较高的制造容差。
