Title: SPP-MIM hybridization meta-film: a biosensing structure uniting the merits of SPR and LSPR Show Chinese title

Title: SPP-MIM混合超薄膜：结合SPR和LSPR优点的生物传感结构单元

Abstract: Having a flat device-solution interface is crucial for nanophotonic biosensors to achieve stable and reproducible performance, by mitigating solid-liquid-gas interfacial processes at the nanometer scale. In this aspect, the metal-insulator-metal (MIM) film presents a capable solution, by hybridizing surface plasmon polaritons (SPP) and MIM gap plasmons, which is enabled by the latter's unique dispersion characteristic and wide tunability. In this meta-film, the SPPs propagate along a flat interface, and seal the gap plasmons which can be integrated with nanostructures, e.g., a coupling grating. In addition, by tuning the gap plasmons, the SPP-MIM hybridization meta-film can be designed to achieve a significantly reduced SPP evanescent depth and a significantly improved surface sensitivity. Using gold as the plasmonic material, such improvements are theoretically predicted across a broad spectral range, from visible to near infrared. Particularly, at 1550 nm, we show that a grating-coupled meta-film device is designed to have its evanescent depth shortened from 1.4 micrometers to 0.16 micrometers, with an enhancement factor of 5.6 in its surface sensitivity, as compared with traditional grating-coupled SPR. This unique characteristic of the SPP-MIM meta-film makes it an efficient combination of propagating SPR and LSPR, by simultaneously having a flat and simple biosensing interface, a short evanescent depth and a high surface sensitivity. It provides an inspiring approach for transforming various LSPR designs into stable biosensors. Show Chinese abstract

Abstract: 拥有平坦的器件-溶液界面对于纳米光子生物传感器实现稳定和可重复的性能至关重要，这通过减轻纳米尺度下的固-液-气界面过程来实现。 在这方面，金属-绝缘体-金属（MIM）薄膜提供了一个有效的解决方案，通过将表面等离子体极化激元（SPP）和MIM间隙等离子体杂化，这是由后者独特的色散特性和宽调谐性所实现的。 在该超材料中，SPP沿平坦界面传播，并密封了可以与纳米结构集成的间隙等离子体，例如耦合光栅。 此外，通过调节间隙等离子体，SPP-MIM杂化超材料可以设计为显著减少SPP的倏逝深度并显著提高表面灵敏度。 使用金作为等离子体材料，这些改进在从可见光到近红外的广阔光谱范围内被理论预测。 特别是，在1550 nm处，我们展示了一种光栅耦合的超材料器件，其倏逝深度从1.4微米缩短到0.16微米，其表面灵敏度的增强因子为5.6，与传统的光栅耦合SPR相比。 SPP-MIM超材料的这一独特特性使其成为传播型SPR和LSPR的有效结合，同时具有平坦且简单的生物传感界面、短的倏逝深度和高的表面灵敏度。 它为将各种LSPR设计转化为稳定的生物传感器提供了一种有启发性的方法。