Excitation of Bloch Surface Waves on an Optical Fiber Tip

The integration of structures supporting Bloch surface waves (BSWs) with optical fibers is highly desirable, since it would enable the development of high-figure-of-merit miniaturized all-fiber optrodes, opening new pathways within the "lab-on-fiber" roadmap. Here, the first experimental demonstration of grating-assisted excitation of BSWs on the tip of single-mode fibers in the near-infrared region is provided. This is attained via fabrication of a 1D diffraction grating on the fiber facet, and subsequent deposition of a 1D photonic crystal. In spite of a resonance broadening due to grating-induced morphological perturbations, the measured Q-factor of 50 is still higher than typical lab-on-tip plasmonic-probe benchmarks. With a view toward biomolecular sensing, a surface sensitivity of 1.22 nm nm of homogeneous overlay deposited over the active region, which is in line with most plasmonic optrodes largely used in connection with optical fibers, is evaluated. The results also highlight the current limitations and the challenges to face for the development of advanced BSW-based fiber-tip platforms for biological sensing applications.