All-Fiber Plasmonic Platform Based on Hybrid Composite Metal/Glass Microwires

Metal tips are emerging plasmonic structures that can offer high field intensity at the tip apex and high confinement on the nanoscale. However, the fabrication of smooth metal tips with well-defined geometrical characteristics, crucial for optimizing the performance of the plasmonic structure, is not trivial. Furthermore, pure metal tips are exposed to the environment and fragile, thus complicating their use in real applications. The proposed platform based on hybrid composite glass metal microwires can offer the required robustness for device development. An optimized fabrication process of high-quality all-fiber plasmonic tips by tapering such hybrid metal core/dielectric cladding microfibers is proposed and demonstrated experimentally. The presence of the dielectric cladding offers continuous re-excitation of the plasmon modes due to repeated total internal reflection at the glass/air interface, which can dramatically reduce the high losses induced by the metal core. This enables direct light coupling from the distal end of fiber instead of side excitation of the tip, allowing thus their integration in the optical fiber and planar circuits. Plasmonic tips were successfully demonstrated in a highly controllable manner, and their performance was related to simulation results predicting high field enhancement factors up to 10(5).