Open AccessFiber-interface directional coupler inscribed by femtosecond laser for refractive index measurements
Author(s) -
Jinli Han,
Yunfang Zhang,
Changrui Liao,
Yuying Jiang,
Ying Wang,
Chupao Lin,
Shen Liu,
Jiachen Wang,
Zhe Zhang,
Jiangtao Zhou
Publication year - 2020
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.390674
Subject(s) - optics , materials science , graded index fiber , polarization maintaining optical fiber , femtosecond , optical fiber , photonic crystal fiber , plastic optical fiber , inscribed figure , laser , fiber , fiber optic sensor , physics , geometry , mathematics , composite material
A novel fiber-interface directional waveguide coupler was inscribed on the surface of a coreless fiber by femtosecond laser, and was successfully applied to highly sensitive refractive index (RI) measurements. The primary arm was first inscribed to couple light from a lead-in single mode fiber to the fiber interface, then back to a lead-out single mode fiber. A side arm was inscribed parallel and in close proximity to the primary arm. Light propagating in the primary arm could then be efficiently coupled into the side arm when a phase-matching condition was met, which produced a dramatic spectral dip at the coupling wavelength. The proposed device achieved a sensitivity as high as ∼8249 nm/RIU over an RI range of 1.44-1.45, due to strong evanescent fields excited in fiber-interface waveguides. The proposed in-fiber directional coupler exhibits high mechanical strength, a compact configuration, and excellent RI sensitivity. As such, it has significant potential for practical applications in biochemical sensing.