Plasmonic enhanced fluorescence via 3D printing spiral conical tapered gold tip bound to optical fiber

We build a 3D printing spiral conical tapered gold tip directly on the end face of an optical fiber as an efficient fluorescence enhancement device via the two-photon polymerization direct laser writing technology and magnetron sputtering technique. At an optimized geometry achieved via three-dimensional finite-difference time-domain numerical simulations, the gold tip allows the incident light coming from the optical fiber to efficiently excite the surface-plasmon polariton at the outer surface and trigger bright fluorescence of Rodamine dye molecules. The experimental results show that when the incident green laser light at 532 nm has an intensity of 0.5 µW, the fluorescence enhancement factor by the spiral tapered gold tip bound to fiber is about 38 times greater than the reference sample of the flat-cleaved gold film coated fiber. This 3D nanostructured gold-tip bound optical fiber may provide a promising way to improve detection sensitivity in fluorescence-based sensing platforms.