Correction method for absorption-dependent signal enhancement by a liquid-core optical fiber.

The enhancement of a dissolved chemical's Raman scattering by a liquid-core optical fiber (LCOF) geometry is absorption dependent. This dependence leads to a disruption of the usual linear correlation between chemical concentration and Raman peak area. To recover the linearity, we augmented a standard LCOF Raman spectroscopy system with spectrophotometric capabilities, permitting sequential measurements of Raman and absorption spectra within the LCOF. Measurements of samples with identical Raman-scatterer concentrations but different absorption coefficients are described. Using the absorption values, we reduced variations in the measured Raman intensities from 60% to less than 1%. This correction method should be important for LCOF-based Raman spectroscopy of sample sets with variable absorption coefficients, such as urine and blood serum from multiple patients.