Metasurfaces, as artificially designed subwavelength structures, have emerged as a highly effective platform for the development of advanced optical devices. Through precise calculation and the design of the periodic structure of the metasurface, the amplitude, phase and polarization state of the incident light can be flexibly adjusted at the micro-nano levels, which have a wide range of applications in wavefront control [1], color filtering [2], metalens [3,4], optical imaging [5,6], lasers [7], polarization detection [8,9] and other fields. The output signal of most optical sensors is directly related to the refractive index of the sample being measured, making the refractive index one of the most commonly measured parameters in optical sensing [10]. Recent studies have demonstrated that metasurfaces are sensitive to changes in the refractive index of the surrounding environment, enabling their application in sensing to achieve rapid, non-contact, and non-destructive detection [11,12]. This approach offers convenience, flexibility, and high detection efficiency.

Metal-dominated surface plasmon resonance has been shown to be extremely sensitive to changes in the refractive index of the surrounding environment [[13], [14], [15]]. However, due to the inherent ohmic losses of metallic metasurface, they usually result in a wider resonance linewidth (FWHM) and lower Q-factor, which to some extent limits their application in micro-nano optoelectronic devices [16]. In contrast, all-dielectric metasurface have the advantages of low loss, CMOS compatibility, broad spectral range, and simple fabrication process [17,18]. To enhance the FOM and sensitivity of the metasurface, high-refractive-index dielectric materials, such as crystalline silicon, germanium, silica, and alumina, are commonly chosen. In addition, by manipulating the geometry, period, dimensions, and arrangement of the dielectric structures, precise control of the local electromagnetic field distribution can be achieved, fulfilling the requirements for low-loss, high-quality sensing [19].

Fano resonances arise from the destructive interference between discrete and continuum states, and high-Q Fano resonances can significantly enhance light-matter interactions, which is crucial for the development of high-performance micro-nano photonic devices [20,21]. Recently, it has been demonstrated that dielectric metasurface excited by bound states in the continuum (BIC) can support high-Q Fano resonances [[22], [23], [24]]. BIC is a unique mode that exists in the continuum spectrum, where the resonance is completely confined within the system and fully decoupled from the far-field radiation continuum [25]. Ideally, BICs exhibit an infinite Q-factor in symmetric nanostructures, making them unobservable in the spectrum due to their vanishing linewidth. In practical applications, symmetry breaking can be introduced into metasurface structures to induce radiative leakage, enabling the excitation of Q-BIC modes with finite Q-factors and narrow linewidths. This provides an effective platform for achieving high-Q Fano resonances. Furthermore, symmetry breaking in metasurfaces introduces additional degrees of freedom, allowing for the manipulation of light polarization properties. The sharp spectral features and polarization selectivity provided by symmetry-protected Q-BICs make optical sensors not only highly sensitive but also capable of distinguishing different analytes based on their optical characteristics [26]. In 2022, Ye et al. designed an all-dielectric metasurface based on diamond-shaped etched holes that excited triple Fano resonances in the near-infrared region, achieving a maximum sensitivity and figure of merit (FOM) of 255 nm/RIU and 477 RIU−1, respectively [27]. In 2023, Keisuke et al. developed a nanocavity crystalline silicon-based metasurface with a Q-factor exceeding 1200 and a sensitivity of 300 nm/RIU [28]. In 2024, Luo et al. proposed a hybrid metal-dielectric metasurface sensor that achieved a high Q-factor of 412 and a sensitivity of 492.7 nm/RIU in the near-infrared region [29]. This precise control offers an effective solution for detecting trace analytes and tiny environmental changes. However, most research tends to focus on single sensing applications with a Q-BIC driving mode, while there is less work on simultaneously optimizing the polarization and sensing properties of metasurfaces. Such limitations have restricted the practical application of existing metasurfaces and prevented them from fully exploiting their potential advantages.

In this paper, we design an all-dielectric metasurface based on Q-BIC composed of periodic crystalline silicon (c-Si) nanorod dimers on SiO2 substrate. In order to ascertain the impact of the nanorod dimer's tilt on the excitation of the Q-BIC mode, the optical properties of the designed structure were analyzed to analysis using the finite element method (FEM). When the nanorod dimers were tilted, three distinct Fano resonance peaks appeared in the near-infrared region. Electromagnetic field analysis and multipole decomposition indicate the dominant modes of these resonances. Fine-tuning the geometric parameters of the metasurface allows for flexible control of the resonance spectrum, making it adaptable for various applications in the near-infrared region. We further investigated the polarization characteristics of the metasurface, and confirming its dynamic tunability and polarization selectivity. This metasurface structure provides a valuable theoretical reference for the development of high-performance refractive index micro-nano sensors, optical switches, and modulators.