Metasurfaces have become a fascinating framework for nonlinear optics, with the advantages of a compact footprint and unprecedented flexibility to manipulate light. However, further advancements are necessary to enhance the efficiency of metasurfaces in nonlinear devices. Here, a novel approach for second harmonic generation (SHG) based on the LiNbO₃ metasurface using leaked plasmonic bound states in the continuum (BIC) is proposed. The behavior of SHG in the guided mode resonance (GMR) under TE polarization and plasmonic modes under TM polarization is investigated. The structure consists of a plasmonic grating overlying a nonlinear lithium niobate dielectric waveguide layer that supports two different BIC, namely plasmonic BIC and GMR BIC. The evolution of second harmonics generation(SHG) near two groups of BIC is explored. The SHG of the plasmonic quasi-BIC is stronger than that based on the GMR quasi-BIC. In addition, the plasmonic accidental quasi-BIC produces stronger harmonic effects than the quasi-BIC based on symmetry-broken. Specifically, at a pump intensity of 30 MW/cm², this accidental quasi-BIC results in SHG efficiency of 1.86 × 10⁻³. This work provides a valuable approach to achieving enhanced SHG using plasmonic and BIC. It opens up new possibilities for the utilization of LiNbO₃ in integrated nonlinear nanophotonics and paves the way for the development of advanced nonlinear photonic devices.

超表面已经成为非线性光学的一个令人着迷的框架，具有紧凑的占地面积和前所未有的操纵光的灵活性的优点。然而，需要进一步的进步来提高非线性器件中超表面的效率。在这里，提出了一种基于LiNbO _{3超表面的二次谐波产生（SHG）的新方法，该方法使用连续体中泄漏的等离子体束缚态（BIC）。}研究了二次谐波在 TE 偏振下的导模共振 (GMR) 和 TM 偏振下的等离激元模式中的行为。该结构由覆盖非线性铌酸锂电介质波导层的等离子体光栅组成，该波导层支持两种不同的 BIC，即等离子体 BIC 和 GMR BIC。探讨了两组 BIC 附近二次谐波产生（SHG）的演变。等离子体准BIC的SHG比基于GMR准BIC的SHG更强。此外，等离子体偶然准BIC比基于对称破缺的准BIC产生更强的谐波效应。^{具体来说，在30 MW/cm 2}的泵浦强度下，这种偶然的准BIC导致SHG效率为1.86 × 10 ^-3。这项工作提供了一种利用等离子体和 BIC 实现增强 SHG 的有价值的方法。_{它为LiNbO 3}在集成非线性纳米光子学中的应用开辟了新的可能性，并为先进非线性光子器件的发展铺平了道路。