On-chip mode converters and multiplexers are fundamental components to scale the capacity of silicon optical interconnects by using different spatial modes of waveguides. Recently, we proposed a low loss and compact mode converter and multiplexer consisting of a subwavelength-engineered multimode interference coupler, tapered waveguides as phase shifter and a symmetric Y-junction. However, the narrow spectral response of the tapered phase shifter limited the device crosstalk performance. In this work, we demonstrate that the use of a subwavelength grating phase shifter with low phase-shift errors substantially reduces the crosstalk and expands the operational bandwidth. A complete multiplexer-demultiplexer link consisting of two devices in back-to-back configuration was fabricated in a 220-nm silicon-on-insulator platform. Experimental measurements of the complete link show insertion loss below 2 dB and crosstalk less than −17 dB over a bandwidth of 245 nm (1427 – 1672 nm).

中文翻译：

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带亚波长移相器的模式转换器和多路复用器，用于扩展宽带操作

片上模式转换器和多路复用器是通过使用不同的波导空间模式来扩展硅光互连容量的基本组件。最近，我们提出了一种低损耗、紧凑的模式转换器和多路复用器，由亚波长设计的多模干涉耦合器、作为移相器的锥形波导和对称 Y 结组成。然而，锥形移相器的窄光谱响应限制了器件的串扰性能。在这项工作中，我们证明了使用具有低相移误差的亚波长光栅移相器大大减少了串扰并扩展了操作带宽。在 220 纳米绝缘体上硅平台上制造了一个完整的多路复用器-多路分解器链路，该链路由两个背对背配置的器件组成。