A high-sensitive refractive index sensor is proposed and demonstrated by utilizing merging bound states in the continuum, namely a set of integer topological charges in the momentum space. Through varying cladding refractive index $n_c$, the topological charges continuously depart from the merging state, and result in the robust and considerable high-$Q$ factors (above $7\times 10^4$) in a large detection range of 0.456. In such a range, sensing sensitivity of $\sim$36 nm/RIU and figure-of-merit from $\sim$5990 (air) to 1607 ($n_c$ = 1.456) are achieved. Meanwhile, the detection limit on the order of $10^{-5}$ RIU is clearly distinguishable from the measured spectrum under tiny variation of cladding refractive index. Our work paves the way for promising integrated high-sensitive sensors in many biological and chemical applications.

中文翻译：

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拓扑电荷演化实现的高灵敏度折射率传感

通过利用连续体中的合并束缚态，即动量空间中的一组整数拓扑电荷，提出并展示了一种高灵敏度的折射率传感器。通过改变包层折射率$n_c$，拓扑电荷不断地离开合并状态，并导致鲁棒的和相当高的$Q$ 因素（以上 $7\乘以 10^4$) 在 0.456 的大检测范围内。在这样的范围内，感应灵敏度为$\sim$36 nm/RIU 和品质因数来自 $\sim$5990（空运）到 1607（$n_c$= 1.456) 达到。同时，检出限为$10^{-5}$在包层折射率的微小变化下，RIU 与测得的光谱明显不同。我们的工作为在许多生物和化学应用中具有前景的集成高灵敏度传感器铺平了道路。