The silicon-based arrayed waveguide grating (AWG) is widely used due to its compact footprint and its compatibility with the mature CMOS process. However, except for AWGs with ridged waveguides of a few micrometers of cross section, any small process error will cause a large phase deviation in other AWGs, resulting in an increasing cross talk. In this paper, an ultralow cross talk AWG via a tunable microring resonator (MRR) filter is demonstrated on the SOI platform. The measured insertion loss and minimum adjacent cross talk of the designed AWG are approximately 3.2 and -45.1 dB, respectively. Compared with conventional AWG, its cross talk is greatly reduced.

为了探究鼎形微环谐振器的耦合区数量对输出的影响，建立了鼎形微环谐振器的物理模型。利用传输矩阵法对鼎形微环谐振器的物理模型进行研究。分析了不同耦合区数量对鼎形微环谐振器输出的影响。实验结果表明，随着耦合区数量的增加，在1.54~1.56 μm工作波长范围内谐振峰的数量增加，半高全宽FWHM越小，品质因子Q则越大，器件的储能性能越好，并且还能实现对特定波长的滤波作用。耦合区数量对鼎形微环谐振器性能有着很大影响，在设计时根据实际需要选择耦合区数量。

为实现高灵敏度及高品质因数的折射率传感特性，设计了一种基于槽型相移布拉格光栅的微环谐振器结构。该结构由槽型直波导内嵌相移布拉格光栅耦合单实波导微环构成。结构中离散态光模式与连续态光模式相互干涉产生了Fano共振。利用传输矩阵法量化谐振器中各部分的光场分布，分析系统的传输原理。采用时域有限差分法对提出的器件结构进行仿真模拟，并对结构物理参数进行优化。模拟结果表明该结构的品质因数达到25 729，比传统微环谐振器提高了3倍以上，消光比为18.65 dB，高出传统微环谐振器6.46 dB，折射率灵敏度达到122 nm/RIU，且该谐振器结构简单。所提出的结构在传感应用中具有一定的优势。

Silicon nitride (Si₃N₄) waveguides with high confinement and low loss have been widely used in integrated nonlinear photonics. Indeed, state-of-the-art ultralow-loss Si₃N₄ waveguides are all fabricated using complex fabrication processes, and all of those reported that high Q microring resonators (MRRs) are fabricated in laboratories. We propose and demonstrate an ultralow-loss Si₃N₄ racetrack MRR by shaping the mode using a uniform multimode structure to reduce its overlap with the waveguide. The MRR is fabricated by the standard multi project wafer (MPW) foundry process. It consists of two multimode straight waveguides (MSWs) connected by two multimode waveguide bends (MWBs). In particular, the MWBs are based on modified Euler bends, and an MSW directional coupler is used to avoid higher-order mode excitation. In this way, although a multimode waveguide is used in the MRR, only the fundamental mode is excited and transmitted with ultralow loss. Meanwhile, thanks to the 180 deg Euler bend, a compact chip footprint of 2.226 mm perimeter with an effective radius as small as 195 μm and a waveguide width of 3 μm is achieved. Results show that based on the widely used MPW process, a propagation loss of only 3.3 dB / m and a mean intrinsic Q of around 10.8 million are achieved for the first time.