Silicon Ultraviolet High-Q Plasmon Induced Transparency for Slow Light and Ultrahigh Sensitivity Sensing

Silicon (Si) plasmonics in the ultraviolet (UV) region owing to its strong UV interband transitions is emerging in the fields of UV nanophotonics and metamaterials. Here, we discuss the narrow plasmon induced transparency (PIT) of a lifted Si nanostrip array and the optical sensing and slow light properties in the UV range. The strong plasmonic hybridization between the broad Si localized surface plasmon (LSP) supported by a lifted Si nanostrip and the narrow optical diffraction mode propagated in air caused by Wood anomaly of a periodic array is achieved and leads to a sharp PIT with the quality (Q) factor being 40 in the UV range. Our calculated PIT effect of the proposed lifted Si nanostrip array is well demonstrated by the coupled oscillator theory. The position and lineshape of the UV PIT tuned by varying structural sizes are further discussed. The large group index of our designed lifted Si nanostrip array is achieved to be about 320 within the UV region. Moreover, the sensitivity (S) and figure of merit (FoM) are obtained to be as large as 295 nm/RIU and 84, respectively. These research results could have significant impact on the realization of multifunctional UV plasmonic nanodevices for such as optical sensor and slow light.