Wu Rui, Wang Xingqi, Qiao Xin, Wei Yong, Liu Yingjie
Opt Express. 2025 Mar 10;33(5):11541-11554. doi: 10.1364/OE.555172.
A compact and scalable mode (de)multiplexer stands as a pivotal component in on-chip mode division multiplexing systems. Subwavelength gratings can flexibly adjust the waveguide refractive index at the subwavelength scale, while inverse design emerges as a promising methodology for optimizing extensive and intricate parameter sets. Here we propose and experimentally demonstrate a compact mode (de)multiplexer using inverse-designed subwavelength grating structures. The proposed six-channel mode (de)multiplexer is designed with an ultra-short coupling lengths (8.4-15 µm for TE-TE channels) and eliminates the adiabatic transition tapers for cascaded asymmetric directional couplers. This design achieves a total length of only 76 µm. The experimental results reveal that the measured peak insertion losses for all mode channels are less than 0.77 dB, and the crosstalk are below -15 dB in a 100 nm waveband. Furthermore, it is very flexible to extend the dual-polarization mode (de)multiplexer. As a proof-of-concept, a dual-polarization mode (de)multiplexer for supporting eight channels (TE-TE and TM-TM modes) is also experimentally demonstrated. This work provides a promising way for on-chip large-scale and dense-integrated polarization and mode division multiplexing circuits.
紧凑且可扩展的模式（解）复用器是片上模式分割复用系统中的关键组件。亚波长光栅可以在亚波长尺度上灵活调整波导折射率，而逆向设计则成为优化大量复杂参数集的一种有前途的方法。在此，我们提出并通过实验证明了一种使用逆向设计的亚波长光栅结构的紧凑模式（解）复用器。所提出的六通道模式（解）复用器设计有超短耦合长度（TE-TE通道为8.4 - 15微米），并消除了级联非对称定向耦合器的绝热过渡锥。这种设计的总长度仅为76微米。实验结果表明，所有模式通道的测量峰值插入损耗小于0.77分贝，在100纳米波段内串扰低于 -15分贝。此外，扩展双偏振模式（解）复用器非常灵活。作为概念验证，还通过实验证明了一种支持八个通道（TE-TE和TM-TM模式）的双偏振模式（解）复用器。这项工作为片上大规模和密集集成的偏振和模式分割复用电路提供了一条有前途的途径。
