Plasmonic Fiber Tip-Enhanced Raman Spectroscopy Based on Shear-Force Near-Field Microscopy

Shear-force feedback-based scanning near-field optical microscopy (SNOM) has emerged as a vital technique for optical characterization at the nanoscale. However, the low energy conversion efficiency of the aperture fiber tip (ATFT) limits their applications in nanospectroscopy. To overcome these challenges, the plasmonic fiber tip (PFT) was integrated into shear-force feedback-based SNOM, thereby establishing the tip-enhanced Raman spectroscopy (TERS) platform. With the fiber radial vector mode (RVM) internally exciting the PFT, the resultant tip nanofocusing light source exhibits a significant enhancement in both the electric-field intensity and the electric-field gradient effect, simultaneously. This advance ensures the resolution of the shear-force topography while obtaining the nanospectral information on the analytes, such as the gradient-field Raman spectrum. The developed fiber-RVM internal excitation-based SNOM-TERS platform holds significant promise for applications in nanophotonics and other fields that require precise spectral characterization at the nanoscale.