Application of liquid-core optical fiber in the measurements of Fourier transform Raman spectra

The application of liquid-core optical fiber (LCOF) in the measurement of Fourier transform Raman spectra (FTRS) can enhance the Raman spectra intensity 102–103 times, and the minimal length of the optical fiber for yielding maximal Raman spectra intensity is the reciprocal of the optical fiber loss coefficient. By using LCOF, β-caroteneʹs 1520 cm−1 Raman line and rhodamineʹs 1524 cm−1 Raman line were observed in their CS2 solutions. These two Raman lines come from the π–π∗ transition of the CC vibration. As β-carotene and rhodamineʹs concentrations decrease, their Raman lines move to long wavelength (red shift), their linewidths narrow and their molar gain coefficients increase.