Multitip-Localized Enhanced Raman Scattering from a Nanostructured Optical Fiber Array

An optical fiber bundle composed of similar to 6000 individual 3 mu m core diameter fibers has been chemically etched to form a regular array of sharp tips, resulting in the confinement of the light reaching the tip apexes of the fibers as demonstrated by near-field optical microscopy. After coating this nanostructure with a gold thin film (30 nm thick), spatially resolved Raman experiments have been perfomed to detect a benzenethiol monolayer adsorbed on the covering gold film. High intensity Raman spectra were observed and localized at the extremities of the tips, demonstrating a surface enhanced Raman scattering (SERS) effect induced by the strong curvature of the metallized tip apexes. The Raman enhancement factor of the nanostructure has been investigated and an average enhancement factor of 2.7 x 10(4) was measured. This opens new avenues for the use of such optical fibers for in situ and endoscopic Raman measurements on complex systems.