Shang Yuling, Deng Shujie, Jiang Hui, Li Chunquan, Huang Guotao, Wu Shaoyun, Song Zhuofan
Appl Opt. 2025 Apr 1;64(10):2470-2477. doi: 10.1364/AO.552017.
A polarization beam splitter (PBS) is a key device for controlling the polarization state of light in photonic integrated circuits (PICs). In this paper, a compact TM-pass/TE-divide PBS based on a thin-film lithium niobate (TFLN) and grating-assisted contra-directional coupler (GACDC) is proposed. The device makes the contra-directional coupling satisfy the phase-matching condition by etching the corrugated strip waveguide on the waveguide sidewall. It is able to separate the two polarization modes of TE and TM, thus realizing the function of polarization beam splitting. The coupling length of the PBS designed in this paper is 209.5 µm. The simulation results at the center wavelength of 1555 nm show that the extinction ratio of the TE(TM) polarization mode is 42.8 dB (21.0 dB), and the insertion loss is 0.56 dB (0.01 dB). Besides, the crosstalk of the contra-directional coupling is ${-}21;{\rm dB}$. The waveguide grating is employed in the device, which makes it independent of the free spectral range, and it has a large tuning range. The design has the advantages of a high extinction ratio and low crosstalk, which is expected to be an indispensable component in future TFLN PICs.
偏振分束器（PBS）是光子集成电路（PIC）中控制光偏振态的关键器件。本文提出了一种基于薄膜铌酸锂（TFLN）和光栅辅助反向耦合器（GACDC）的紧凑型TM通/TE分PBS。该器件通过在波导侧壁蚀刻波纹状条形波导，使反向耦合满足相位匹配条件。它能够分离TE和TM两种偏振模式，从而实现偏振分束功能。本文设计的PBS耦合长度为209.5 µm。在中心波长1555 nm处的仿真结果表明，TE（TM）偏振模式的消光比为42.8 dB（21.0 dB），插入损耗为0.56 dB（0.01 dB）。此外，反向耦合的串扰为-21 dB。该器件采用了波导光栅，使其与自由光谱范围无关，且具有较大的调谐范围。该设计具有高消光比和低串扰的优点，有望成为未来TFLN PIC中不可或缺的组件。
