A Raman probe was set up with optical fibers and a graded refractive index (GRIN) lens. It was found that the Raman background arising from optical fiber was spatially dependent, while normal Raman (NR) scattering, surface-enhanced Raman scattering (SERS), and surface-enhanced resonance Raman scattering (SERRS) were spatially independent. Spatial optimization was carried out to minimize the background interference of the optical fiber Raman probe with the use of benzoic acid as a test sample. The best configuration of the probe could also be applied to both SERS and SERRS. SER spectra of p-nitrophenol (1.0 × 10-3 M) and SERR spectra of methyl red (1.0 × 10-6 M) were obtained with the use of this probe to check its performance.
Jiayig Ma and Ying-Sing Li, "Optical-Fiber Raman Probe with Low Background Interference by Spatial Optimization," Appl. Spectrosc. 48, 1529-1531 (1994)