A simple Raman multipass capillary cell (MCC) is described that gives 12- to 30-fold signal enhancements for non-absorbing gases. The cell is made by coating the inside of 2-mm inner diameter silica capillary tubes with silver. The device is very small and suitable for remote and <i>in situ</i> Raman measurements with optical fibers. Application of the MCC is similar to previously described liquid core waveguides but, unlike the latter devices, the MCC is generally more applicable to a wide range of non-absorbing gases.
Vol. 3, Iss. 4 Virtual Journal for Biomedical Optics
William F. Pearman, J. Chance Carter, S. Michael Angel, and James Wai-Jeung Chan, "Multipass Capillary Cell for Enhanced Raman Measurements of Gases," Appl. Spectrosc. 62, 285-289 (2008)