High-sensitive refractive index sensing enabled by topological charge evolution
2020
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.
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