3D printing of fiber-integrated plasmonic micro-grating tip enabling high-resolution real-time and in-site refractive index sensing

作者：Huang, Rongtao; Long, Li; Deng, Qiurong; Li, Zhi-Yuan^*

来源：Optics and Laser Technology, 2023, 167: 109796.

DOI：10.1016/j.optlastec.2023.109796

• 3D printing
• Optical fiber
• Surface plasmon resonance
• Real-time and in -site sensing

We design and fabricate a three-dimensional (3D) spiral-grating tapered conical gold tip on an optical fiber end face to serve as a refractive index (RI) sensing probe via a 3D printing technology based on the two-photon polymerization direct laser writing method. The active region of conical tip only has a volumetric size of 14 x 10 x 10 & mu;m3, but inherits the merit of classical planar prism or grating surface plasmon resonance (SPR) optical sensor and enables SPR enhanced micro-zone RI sensing. The experimental results show that this fiber probe has high sensitivity of 333 nm/RIU, high spatial resolution of 10 & mu;m, and fast response speed of 20 ms, and thus can be used to detect and monitor many real-time and in-site RI transition processes. We have successfully used this high temporal-spatial resolution optical-sensing fiber probe to monitor water-ethanol solution con-vection process and measure the refractive index distributions across thin interfacial layers in three stratified liquid systems. This SPR enhanced gold tip fiber RI sensor has simultaneously small activity region, simple while sound working principle, easy and robust operation performance, high RI sensitivity, high signal-to-noise ratio, and good mechanical reliability, thus manifests promising potential for real-time and in-situ chemical and bio-logical sensing and detection with fast response speed and excellent spatial resolution.