Abstract
A low-cost and highly accessible method for high sensitivity label-free Raman spectroscopy based on a cylindrical metalized microfiber internally excited via a radially polarized beam (RPB) has been developed. A silver (Ag)-pyramid coated microfiber was designed to be matched with the RPB. Simulation results show that the enhancement of the electric-field intensity of the cylindrically metalized microfiber excited by the RPB can reach a factor of 2.5 × 103, which is much higher than that of linearly polarized beam (LPB) excitation. In experiments, the RPB is directly generated in the optical fiber by converting the LPB to an RPB using electrically controllable, low cost acoustic-optical technology. An Ag-pyramid coated microfiber with ∼9.6 µm diameter was prepared using a simple Ag-mirror reaction. The Raman intensity for malachite green (MG) detected by the Ag-pyramid coated microfiber under RPB excitation was 5 times stronger than that under LPB excitation. The Raman sensitivity for MG in the case of RPB excitation was as low as 10−10 M, a concentration level which was not detectable for LPB excitation. The sensor system gave high repeatability and reliability and should find application in high sensitivity label-free detection in optical sensing with the advantages of low-cost and ease of operation.
Highlights
Optical fibers are one of the most widely used light-guiding components in both industry and fundamental research due to attractive features such as low interference, low noise, and easy integration
The Ag-pyramid coated microfiber was designed to be matched with the radially polarized beam (RPB)
The chemical deposition step was performed for 30 min, and Ag nanostructures were deposited on the surface of the microfiber, the shapes of which were characterized by optical microscopy, as shown in Fig. 2(b); the surface topography was characterized by scanning electron microscope (SEM) as revealed by Figs. 2(c) and 2(d)
Summary
Optical fibers are one of the most widely used light-guiding components in both industry and fundamental research due to attractive features such as low interference, low noise, and easy integration. One of the most important advances is fiber-based surface enhanced Raman spectroscopy (SERS), which opens up new avenues for label-free detection by offering high-resolution Raman spectral information. Fiber-based SERS is based on the synergy of the optical fiber and the noble metal nanostructures, where the light-matter interaction can be enhanced significantly because of the localized surface plasmon resonance (LSPR) induced electric-field enhancement effect, which dominates the SERS mechanism. Research on using different optical modes of the excitation light to illuminate SERS substrates has opened up new opportunities for ultrasensitive Raman detection due to the dependency of the localized surface plasmon modes on the polarization and energy distribution of the excitation light.. Different optical modes of the excitation light have been applied to Raman spectroscopy Research on using different optical modes of the excitation light to illuminate SERS substrates has opened up new opportunities for ultrasensitive Raman detection due to the dependency of the localized surface plasmon modes on the polarization and energy distribution of the excitation light. In free space, different optical modes of the excitation light have been applied to Raman spectroscopy
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
