Melikyan Argishti, Kim Kwangwoong, Fontaine Nicolas, Chandrasekhar Sethumadhavan, Chen Young-Kai, Dong Po
Opt Express. 2018 Jul 9;26(14):18523-18531. doi: 10.1364/OE.26.018523.
Electro-magnetic (EM) mixers are fundamental building blocks in communication systems. They are used in frequency/wavelength filters, interferometric modulators, amplitude-phase receivers, to name a few. Traditional EM mixers have two or more input ports and work only for co-polarized signal and local-oscillator (LO) incident on its inputs. Here we report on novel designs, in silicon, of inter-polarization EM mixers operating at 1550 nm wavelength. The 180-degree optical mixer comprising a single input port is demonstrated to coherently mix orthogonally polarized signal and LO. Using the proposed 180-degree mixer, we report on a novel design for a 90-degree optical mixer on silicon with small footprint, broadband response, low loss and good fabrication tolerance. It exploits birefringence of a waveguide to achieve broadband and fabrication-tolerant 90° phase difference between the signal/LO relative phase in the in-phase and quadrature components. A monolithic silicon photonics coherent receiver is demonstrated using the reported 90-degree mixer, and its operation at 22 Gbaud and 44 Gbaud is shown. These mixers pave the way for novel coherent receiver architectures in long-haul, metro, passive optical networks and data-center interconnect applications.
电磁（EM）混频器是通信系统中的基本组件。它们用于频率/波长滤波器、干涉调制器、幅度 - 相位接收器等。传统的EM混频器有两个或更多输入端口，并且仅适用于共极化信号和本地振荡器（LO）入射到其输入端口的情况。在此，我们报告了在硅中设计的、工作在1550纳米波长的新型交叉极化EM混频器。包含单个输入端口的180度光混频器被证明能够相干地混合正交极化信号和本地振荡器信号。利用所提出的180度混频器，我们报告了一种在硅上设计的新型90度光混频器，它具有小尺寸、宽带响应、低损耗和良好的制造容差。它利用波导的双折射来实现同相和正交分量中信号/本地振荡器相对相位之间的宽带且具有制造容差的90°相位差。使用所报道的90度混频器展示了一种单片硅光子学相干接收器，并展示了其在22 Gbaud和44 Gbaud下的运行情况。这些混频器为长途、城域、无源光网络和数据中心互连应用中的新型相干接收器架构铺平了道路。
