Enhancement of Raman signal
Raman spectroscopy has been applied to biochemical studies. The Raman signal of biomolecules is often weaker than the contribution from H2O, and therefore, careful experiment and data analysis has been required. Raman spectroscopy will be utilized more in this field by improving the sensitivity of the signal detection. We made a unit to make a vertical flow column of the sample solution (vertical flow apparatus, Figures(a and a')). Using Raman microscope, we introduced the excitation beam from the top of the column. This setup allowed the enhancement of Raman signal up to 12 times and enabled the efficient sampling (Fig. (b)). The enhancement factor is proportional to an inverse of the diameter of pinhole (Fig. (c)). The total reflection of the excitation beam and the generated Raman signal in the column explains the enhancement, since the sample column acts as core of an optical fiber surrounded by "air" as the cladding material.

[1] H.Hiramatsu and T.Saito, Journal of Raman Spectroscopy 2014, 45, 208-210.