We present a novel design for an all-dielectric metasurface ultra-sensitive refractive index (RI) sensor, characterized by a high-quality factor (Q_f) and figure of merit (FOM). This design incorporates two high-order toroidal modes, including electric toroidal quadrupole (\(\:{Q}_{T}^{e}\)​) and magnetic toroidal quadrupole (\(\:{Q}_{T}^{m}\)​) based on quasi‑bound states in the continuum (q-BIC) resonances. Our findings demonstrate the feasibility of switching between \(\:{Q}_{T}^{e}\) and \(\:{Q}_{T}^{m}\)​ through various symmetry-breaking mechanisms. To excite these high-order toroidal modes, we explored several symmetry-breaking strategies, including complex structural designs, symmetry disruption, and variations in the incident wave angle. Symmetry breaking in the structure induces new modes in the transmission spectrum, which are highly advantageous for sensing applications due to the presence of dark modes. The designed metasurface exhibits the capability to sense a broad range of RI in diverse environments, particularly in biochemical fields. Sensitivity (S) is significantly enhanced by the excitation of new resonance modes and adjustments in the incidence angle, increasing from 217 GHz/RIU in a symmetrical structure to 512.3 GHz/RIU for \(\:{Q}_{T}^{e}\)​. The FOM improves from 197 RIU¹ to 8538 RIU^− 1 for \(\:{Q}_{T}^{e}\)​ and 152,395 RIU^− 1 for \(\:{Q}_{T}^{m}\)​. Additionally, the Q_f rises from 872 to 17,983 and 921,351 for \(\:{Q}_{T}^{e}\)​ and \(\:{Q}_{T}^{m}\)​, respectively.

我们提出了一种全介电超表面超灵敏折射率 （RI） 传感器的新设计，其特点是高品质因数 （Q_f） 和品质因数 （FOM）。该设计结合了两种高阶环形模式，包括电环形四极子 （\（\：{Q}_{T}^{e}\）） 和磁环形四极子 （\（\：{Q}_{T}^{m}\）） 基于连续谱 （q-BIC） 共振中的准束缚态。我们的研究结果证明了通过各种对称性打破机制在 \（\：{Q}_{T}^{e}\） 和 \（\：{Q}_{T}^{m}\） 之间切换的可行性。为了激发这些高阶环形模式，我们探索了几种打破对称性的策略，包括复杂的结构设计、对称性破坏和入射波角度的变化。结构中的对称性打破会在透射光谱中感应出新的模式，由于暗模式的存在，这对传感应用非常有利。设计的超表面表现出在不同环境中感知广泛 RI 的能力，尤其是在生化领域。灵敏度 （S） 通过激发新的谐振模式和调整入射角而显著提高，从对称结构中的 217 GHz/RIU 增加到 \（\：{Q}_{T}^{e}\） 的 512.3 GHz/RIU。\（\：{Q}_{T}^{e}\） 的 FOM 从 197 RIU ¹ 提高到 8538 RIU^{− 1}，\（\：{Q}_{T}^{m}\） 的 FOM 从 152,395 RIU− 1 提高到 152,395 RIU^{− 1}。此外，\（\：{Q}_{T}^{e}\） 和 \（\：{Q}_{T}^{m}\） 的 Q_f 分别从 872 上升到 17,983 和 921,351。