Cheng Wei, Lin Dongdong, Liu Pengcheng, Yun Binfeng, Lu Mengjia, Shi Shangqing, Hu Guohua, Cui Yiping
Opt Express. 2022 Dec 19;30(26):46147-46156. doi: 10.1364/OE.477261.
Fano resonance with asymmetric line shape is very promising in many applications such as optical switching, sensing, slow light, laser. Fano resonances based on some integrated structures have been demonstrated on the silicon on insulator platform. However, the extinction ratios and slope rates of the most proposed integrated Fano resonances are relatively low, which limits their applications. In this paper, a tunable silicon nitride coupled resonator optical waveguide (CROW) embedded in a Mach-Zehnder interferometer (MZI) is proposed to achieve Fano resonance. Benefiting from fine tuning supported by the low thermo-optic coefficient of the silicon nitride optical waveguide, the optical amplitudes and phases in the two arms of the MZI were accurately adjusted to achieve destructive interference, which gives an ultra-high extinction ratio. Furthermore, high quality factor CROW, supported by the native low loss silicon nitride optical waveguide, greatly shrinks the resonance bandwidth. Combining the above two superiorities, a Fano resonance with a very high extinction ratio of up to 57 dB and slope rate as high as 8.1 × 10 dB/nm was obtained, which is an order of magnitude larger than the reported integrated Fano resonances. We believe that the proposed structure would be a promising candidate for high-performance switching and high-sensitivity sensing.
具有非对称线形的法诺共振在诸如光开关、传感、慢光、激光等许多应用中非常有前景。基于一些集成结构的法诺共振已在绝缘体上硅平台上得到证实。然而，大多数提出的集成法诺共振的消光比和斜率相对较低，这限制了它们的应用。本文提出了一种嵌入马赫-曾德尔干涉仪（MZI）中的可调谐氮化硅耦合谐振器光波导（CROW）来实现法诺共振。受益于氮化硅光波导热光系数低所支持的精细调谐，MZI两臂中的光振幅和相位被精确调整以实现相消干涉，从而获得超高消光比。此外，原生低损耗氮化硅光波导所支持的高品质因数CROW极大地缩小了共振带宽。结合上述两个优势，获得了消光比高达57 dB且斜率高达8.1×10 dB/nm的法诺共振，这比已报道的集成法诺共振大一个数量级。我们相信所提出的结构将是高性能开关和高灵敏度传感的有前途的候选者。
