Dielectric optical fiber meta-tip for labeled biosensing.

In the framework of Lab-On-Fiber sensing technology, the integration of Metasurfaces (MSs) on the tip of the optical fiber (Optical Fiber Meta-Tip, OFMT) has represented a major breakthrough. Indeed, we showed that a suitably designed plasmonic OFMT biosensor significantly outperforms standard plasmonic ones due to the advanced light wave manipulation of MSs. To further reduce the limit-of-detection, we propose optrodes for fluorescence enhancement (FE) based on dielectric OFMT. We envision a single fiber probe with a silicon MS integrated on its tip as a light coupled substrate that illuminates the sample and simultaneously collects the enhanced emission from the dye molecules labeling the biological target. We computed numerically the FE factor of a dye molecule for different silicon MSs, obtaining a maximum value of $\sim 1000$. We verified that the dielectric MSs could be realized via electron beam lithography and reactive ion etching on the fiber tip, thus realizing the first dielectric OFMT. This contribution provides the main guidelines for the design and development of advanced LOF devices based on the fluorescence enhancement for labeled biosensing applications.