Kompetenzzentrum für optische Spezialfasern

The combination of Raman spectroscopy with fiber optic probes enables analyzing the biochemical composition of tissues without markers in a non-destructive way. A small diameter (1 mm) fiber optic probe with one excitation fiber, 11 detection fibers and integrated filters (Emvision, USA) was recently coupled to a Raman spectrometer (Kaiser Optical Systems) to study excised arteries ex vivo and rabbit arteries in vivo. The current contribution introduces a novel fiber optic Raman probe with in-line fiber Bragg gratings (FBGs) as notch filter in the collection path. Multi-core single-mode fibers (MCSMF) were drawn integrating 19 and 61 single-mode cores to improve collection efficiency. Raman probes were assembled with one fiber for excitation and six MCSMF with inscribed FBGs for collection. The diameter of the 6 around 1 geometry can be reduced down to 0.375 mm. Background suppression, collection efficiency and distance dependence of the probes were characterized and first Raman measurements are presented. The advantages of the novel probes are discussed and further applications to Raman-on-chip detection schemes are described.