Seven-core fiber SPR sensor

Abstract

An optical fiber refractive index sensor with six detection ranges is realized by integrating six microfibers surface plasmon resonance (SPR) sensors on the facet of seven-core optical fiber via the 3D micro- and nanoarchitectures fabrication technology of two-photon lithography. Although optical fiber SPR sensors show advantages of miniaturization, lightweight, flexibility and high sensitivity, their detection ranges are normally narrow and fixed and are hardly being changed. In this work, we proposed a strategy to expand the detection ranges almost six times than a traditional single optical fiber SPR sensor, i.e., integrating six microfibers SPR sensors on the facet of a seven-core optical fiber. Six microfibers with arc shape are directly fabricated on top of the facets of the seven-core optical fiber via two-photon lithography. All of the six arched microfibers are connected into the center core while with the left six ends connected with the other around six cores of the seven-core fiber. A thin spherical shield with its top being designed with flat surface is also fabricated over the six arched microfibers. The top of the arched microfibers is contact with the flat part of the thin spherical shield tangentially. Finally, a thin gold layer is deposited on the spherical shield. When light is coupled into the microfibers, SPR on the gold film will be excited, therefore, integrated six microfiber SRP sensors are achieved on top of the seven-core optical fiber. The resonant wavelength of the SPR could be tuned by changing the diameter of the microfiber. Six detection ranges could be obtained by properly design the diameters of the six microfibers. Such six detection ranges optical fiber SPR sensor provide more convenient for SPR sensing, for example, different analytes with much refractive index differences could be analysized only by one spectrometer, and if the six microfiber SPR are functionalized with different bio-molecular, such senor could be used to detect different targets in the same time and real-time.