High-Sensitive Refractive Index Sensing Enabled by Topological Charge Evolution

• Published in: IEEE photonics journal Vol. 12; no. 5; pp. 1 - 10
• Main Authors: Lv, Jiaxin, Chen, Zihao, Yin, Xuefan, Zhang, Zixuan, Hu, Weiwei, Peng, Chao
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.10.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: bound state in the continuum; Cladding; high-<inline-formula xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <tex-math notation="LaTeX"> Q</tex-math> </inline-formula> resonance; Merging; optical sensor; Optical sensors; Photonic crystal; Refractive index; Refractivity; Scattering; Sensitivity; topological charge; Topology; Wavelength measurement
• ISSN: 1943-0655; 1943-0655; 1943-0647
• DOI: 10.1109/JPHOT.2020.3017806

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 <inline-formula><tex-math notation="LaTeX">n_c</tex-math></inline-formula>, the topological charges continuously depart from the merging state, and result in the robust and considerable high-<inline-formula><tex-math notation="LaTeX">Q</tex-math></inline-formula> factors (above <inline-formula><tex-math notation="LaTeX">7\times 10^4</tex-math></inline-formula>) in a large detection range of 0.456. In such a range, sensing sensitivity of <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula>36 nm/RIU and figure-of-merit from <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula>5990 (air) to 1607 (<inline-formula><tex-math notation="LaTeX">n_c</tex-math></inline-formula> = 1.456) are achieved. Meanwhile, the detection limit on the order of <inline-formula><tex-math notation="LaTeX">10^{-5}</tex-math></inline-formula> 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.