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

Abstract

Metal tips are emerging plasmonic structures that can offer high field intensity at the tip apex and high confinement in the nanoscale. The fabrication though 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 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 .

Microspheres Formation in a Glass–Metal Hybrid Fiber System: Application in Optical Microwires

“…The breakup time calculated by the simulations was found to be longer than the time estimated from the Tomotika model due to Tomotika’s assumption of an unbound surrounding medium. This is in accordance with our previous experimental results [6], where the breakup of the core was prevented during the post-processing of the microfibers towards the fabrication of fiber tips, as described above. For the short time scales estimated by the Tomotika model, this would not be feasible with our experimental setup (Figure 1), due to the limited velocity of the flame.…”

“…Although the drawing of fibers containing base metals has already been investigated [5], the study of fibers containing noble metals is of intense interest for plasmonic devices. The manufacturing and post processing [6,7] of such fibers though is quite challenging due to the combination of materials with different mechanical and physicochemical properties. At high temperature processing conditions, a number of instabilities induce various microfluidic phenomena leading in turn to formation of various embedded microstructures.…”

“…In the present study, the investigated platform consists of a gold core with a surrounding borosilicate glass cladding with typical diameters of 4 μm and 40 μm, respectively. It was chosen to organise this theoretical study around a specific composite fiber-optic platform, as it served as a motivation engineering case that could also allow comparison of the findings with recently obtained experimental results [6].…”

“…The temperature profile can be adjusted by changing the flow rates of the gases, as well as the distance between the fiber and the flame. Appropriate conditions, such as the velocity and temperature of the heating element, as well as the pull rate of the fiber, can lead to the fabrication of smooth plasmon tips with the desirable geometrical characteristics [6]. In this direction, microfluidic simulations of the tapering process were performed for the determination of the appropriate conditions that would allow the development of plasmonic tips.…”

Design and Implementation of Fiber-embedded Plasmonic Structures in Microwires

“…The proposed platform based on hybrid microwires composed of metal core and silicate glass cladding offers the required robustness and flexibility for engineering and developing plasmonic devices in all-fiber form [3]. 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 and allow long propagation distances.…”