An ultra-broadband mode splitter is proposed based on the phase controlling of the bridged subwavelength grating (BSWG) waveguides. An asymmetric directional coupler composed of two BSWG waveguides with an identical waveguide-width but two different bridge-widths is introduced to split the TM0 and TM1 modes based on the mode-sensitive phase-matching condition. The proposed mode splitter is optimized by utilizing the 3D full-vectorial finite difference time domain method. The results indicate that the proposed mode splitter can achieve a compact coupling length of 5.75 μm, the insertion losses of 0.41 dB and 0.53 dB, and the mode crosstalks of −19.6 dB and −27.8 dB for the TM0 and TM1 modes, respectively. The broad bandwidths of 430 nm and 372 nm can be achieved with the mode crosstalk of ≤−15 dB for the TM0 and TM1 modes, respectively. The fabrication tolerances are also studied in detail. The proposed mode splitter could be employed for signal selection and routing in the mode division multiplexing networks.

中文翻译：

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基于桥接亚波长光栅相位控制的超宽带分模器

基于桥接亚波长光栅（BSWG）波导的相位控制，提出了一种超宽带模式分离器。引入了由两个具有相同波导宽度但两个不同桥宽的 BSWG 波导组成的非对称定向耦合器，以基于模式敏感相位匹配条件分离 TM0 和 TM1 模式。所提出的模式分离器通过利用 3D 全矢量有限差分时域方法进行了优化。结果表明，所提出的模式分离器可以实现 5.75 μm 的紧凑耦合长度，0.41 dB 和 0.53 dB 的插入损耗，以及 TM0 和 TM1 模式的模式串扰分别为 -19.6 dB 和 -27.8 dB。TM0 和 TM1 模式的模式串扰分别为 ≤−15 dB，可以实现 430 nm 和 372 nm 的宽带宽。还详细研究了制造公差。所提出的模式分离器可用于模分复用网络中的信号选择和路由。