title: High-sensitivity four-layer polymer fiber-optic evanescent wave sensor.
abstract: We present a novel four-layer structure consisting of bottom, second, third, and surface layers in the sensing region, for a D-shaped step-index fiber-optic evanescent wave (FOEW) sensor. To reduce the background noise, the surface of the longitudinal section in the D-shaped region is coated with a light-absorbing film. We check the morphologies of the second and surface layers, examine the refractive indices (RIs) of the third and surface layers, and analyze the composition of the surface layer. We also investigate the effects of the thicknesses and RIs of the third and surface layers and the LA film on the light transmission and sensitivity of the FOEW sensors. The results highlight the very good sensitivity of the proposed FOEW sensor with a four-layer structure, which reached -0.077 (μg/l)-1in the detection of the target antibody; the sensitivity of the novel FOEW sensor was 7.60 and 1.52 times better than that of a conventional sensor with a core-cladding structure and an FOEW sensor with a three-layer structure doped with GeO2. The applications of this high-sensitivity FOEW sensor can be extended to biodefense, disease diagnosis, and biomedical and biochemical analysis.
authors.affiliation: Chongqing Key Laboratory of Fiber Optic Sensor and Photodetector, Chongqing Key Laboratory of Modern Photoelectric Detection Technology and Instrument, Chongqing Energy Internet Engineering Center, Chongqing University of Technology, Chongqing 400054, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Xin
authors.affiliation: Chongqing Key Laboratory of Fiber Optic Sensor and Photodetector, Chongqing Key Laboratory of Modern Photoelectric Detection Technology and Instrument, Chongqing Energy Internet Engineering Center, Chongqing University of Technology, Chongqing 400054, China. Electronic address: zhongnianbing@163.com.
authors.forename: Nianbing
authors.initials: N
authors.lastname: Zhong
authors.affiliation: Key Laboratory of Low-grade Energy Utilization Technologies and Systems (Chongqing University), Ministry of Education, Chongqing 400030, China. Electronic address: lqzx@cqu.edu.cn.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Liao
authors.affiliation: Chongqing Key Laboratory of Fiber Optic Sensor and Photodetector, Chongqing Key Laboratory of Modern Photoelectric Detection Technology and Instrument, Chongqing Energy Internet Engineering Center, Chongqing University of Technology, Chongqing 400054, China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Cen
authors.affiliation: Chongqing Key Laboratory of Fiber Optic Sensor and Photodetector, Chongqing Key Laboratory of Modern Photoelectric Detection Technology and Instrument, Chongqing Energy Internet Engineering Center, Chongqing University of Technology, Chongqing 400054, China.
authors.forename: Ruohua
authors.initials: R
authors.lastname: Wu
authors.affiliation: Chongqing Key Laboratory of Fiber Optic Sensor and Photodetector, Chongqing Key Laboratory of Modern Photoelectric Detection Technology and Instrument, Chongqing Energy Internet Engineering Center, Chongqing University of Technology, Chongqing 400054, China.
authors.forename: Zhengkun
authors.initials: Z
authors.lastname: Wang
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000032:analysis / Q000276:immunology; D001453:Balsams / Q000737:chemistry; D015374:Biosensing Techniques / Q000295:instrumentation*; D004338:Drug Combinations; D004867:Equipment Design; D005336:Fiber Optic Technology / Q000295:instrumentation*; D005857:Germanium / Q000737:chemistry; D006041:Goats; D006171:Gutta-Percha / Q000737:chemistry; D007074:Immunoglobulin G / Q000032:analysis / Q000276:immunology; D051379:Mice; D055100:Optical Fibers; D011108:Polymers / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D000888:Antibodies, Anti-Idiotypic; D001453:Balsams; D004338:Drug Combinations; D007074:Immunoglobulin G; D011108:Polymers; D005857:Germanium; C040516:germanium oxide; C029585:Kloroperka; D006171:Gutta-Percha; D015034:Zinc Oxide
keywords: Canada balsam; Fiber-optic evanescent wave sensor; Four-layer structure; GeO(2) nanoparticle; Mouse IgG; Sensitivity