Investigation of optical fiber-tip probes for common and ultrafast SERS

Abstract

In this study, we performed a three-dimensional computational experiment on ultrashort pulse propagation in an optical fiber-tip probe that is decorated with gold nanoparticles (NPs) using a constant structure for the probe's dielectric taper and different spatial configurations of the gold nanoparticles. Interestingly, a hot spot with the highest amplitude of the electric field was found not along the same chain of the NPs but between terminal NPs of neighboring chains of NPs at the probe's tip (the amplitude of the electric field in the hot spots between the NPs along the same chain was of the order of 10 1 , while that between terminal NPs of neighboring chains was of the order of 10 3 ). We eventually identified a configuration with only six terminal nanoparticles (Config4) which is characterized by the highest electric field amplitude enhancement and can provide the highest spatial resolution in the SERS interrogation of an object of interest. The ultrashort temporal responses of the hot spots for all configurations exhibited relatively high pulse elongation (relative elongation was greater than 4.3%). At the same time, due to the reflection of the incident pulse and consequent interference, the temporal responses of most hot spots contained several peaks for all configurations except for the optimum Config4. Nonetheless, the ultrashort temporal responses of all hot spots for Config4 were characterized by a single peak but with a relatively large pulse elongation (relative elongation was 234.1%). The results indicate that further examination of this new structure of a nanoparticles-coated optical fiber-tip probe with only six terminal NPs may provide attractive characteristics for its practical applications.

Numerical Calculation of the Light Propagation in Tapered Optical Fibers for Optical Neural Interfaces

“…One of the most recent approaches to expand the functionalities of optical fibers consists in modifying the endface or the tip of tapered optical fibers to include different types of structures that interact with the incident light in intriguing ways [17,18]. For example, several studies demonstrate that the use of plasmonic structures surrounding the fiber could help confine and concentrate light at the nanoscale [19,20,21,22]. Also, structures made of high-index dielectrics [23] or metals [24] have been shown to enable sub-diffraction light confinement.…”

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

“…The FDTD method are also applicable to the design of gas ber probes to analysis of the electric eld distribution and polarization properties, and the interpretation of the physical mechanisms [19,20]. The three-dimensional computation numerical can be used to pinpoint the location of hot spots on the probe surface and to analyze the ultrashort pulse propagation of the tapered optical ber probe [21]. Both the above theoretical and experimental studies show that the higher SERS sensitivity of the probe are strongly in uenced by ber geometry, and the NPs.…”

Numerical calculation of the light propagation in tapered optical fibers for optical neural interfaces

“…17,18 Several studies demonstrate that the use of plasmonic structures surrounding the fiber could help confine and concentrate light at the nanoscale. [19][20][21][22] Also, structures made of high-index dielectrics 23 or metals 24 have been shown to enable sub-diffraction light confinement. These studies usually assume single-mode optical fibers and therefore do not consider the modedivision demultiplexing of guided light in tapered optical fibers.…”