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Researchers have paid great attention to pursuing metal‐free nanostructures as alternatives to metallic counterparts in the field of surface‐enhanced Raman scattering (SERS) for label‐free sensing. However, these metal‐free investigations are hindered by the tiny enhancement factor of the local near field. Here, the design of all‐dielectric SERS metasurfaces is proposed with quasi‐bound states in the continuum (Q‐BIC), inspired by transformer‐based deep learning. By manipulating the incident angle, the mechanism of strong coupling Q‐BIC is introduced with a large Rabi splitting of ≈105 meV, which opens a bandgap and forms an anti‐crossing behavior. Compared to conventional approaches, the strong coupling Q‐BIC scheme not only boosts an extraordinary SERS enhancement factor of ≈107 but also extends the field‐enhancing scale up to ten‐fold. The theoretical optimization implies overwhelming dominance versus the conventional metallic nanostructure design for SERS. The study denotes an approach to utilize the strong coupling effects of Q‐BIC in all‐dielectric SERS metasurfaces and will provide essential design guides for more powerful sensing applications based on SERS. [ABSTRACT FROM AUTHOR]

Plasmonic metamaterials are receiving increasing attentions due to their great ability to confine light energy at the nanoscale for perfect absorption and various applications in the near infrared and visible region. However, the common practices to achieve the tunable absorption are to adjust the morphology of plasmonic metamaterials. This strategy has a low fabrication efficiency, which limits the applications of plasmonic metamaterials. Here, the absorption efficiency and peak position of the plasmonic metamaterial consisting of Au nanohole array/SiO2 spacer/Au film are tuned by simply controlling the thicknesses of the hexagonal Au nanohole array and the spacer layer, respectively. An ultrahigh absorption of ≈99% and a high surface‐enhanced Raman scattering (SERS) effect (with an average surface enhancement factor of 106) are achieved at the desired laser wavelength. The substrate can be as large as 10 mm in diameter and shows a high uniformity for SERS detection. This work provides a simple way to flexibly tune the optical properties of plasmonic metamaterials for various promising applications such as plasmon‐mediated chemical reactions and biosensing. [ABSTRACT FROM AUTHOR]