Design and Optimization of Tapered Optical Fiber Probes for SERS Utilizing FDTD Method

Abstract

In this work, we report a strategy of Ag nanoparticles (Ag NPs) coated tapered optical ber probes by nite difference time domain (FDTD) simulations. Investigation shows that the ber tip decorated Ag NPs have excellent electric eld enhancement and con nement of light capabilities compared with ber tips. Moreover, we demonstrate the effect of key parameters such as tip radius, conical angle, Ag NPs size and gaps between them on the eld enhanced utilizing typical excitation wavelength of 532, 633 and 785 nm. To further improve the electrical eld effect, a noble metal substrate is introduced below the tip apex which exhibits a higher eld enhancement generated by tip-substrate coupling. The presence of the Au substrate does not lead to a signi cant change in the plasma characteristic peak of the probes at 490 nm. This study provides a useful reference for the fabrication of tapered optical ber with plasmonic nanostructures and the design of robust tapered ber-optic Raman sensors.