Review of optical fibre probes for enhanced Raman sensing

Raman scattering is a photon‐molecular interaction based on the kinetic modes of an analyte. It offers unique fingerprint‐type signals that allow molecular identification. A serious challenge frequently encountered in Raman measurements arises from the requirements of fast, real‐time remote sensing, fluorescence suppression, ultra‐micro concentration detection, small sample volumes and label‐free biological specimens. This review focuses on fibre‐optic probes for Raman spectroscopy, especially for enhanced sampling applications. It aims at providing an overview over contemporary technology and recent excellent researches, and helps identifying future developments necessary to bring the emerging technology to instrument manufacturers and end users. After a short introduction to surface‐enhanced Raman scattering technology, professional algorithms for design optimization of the fibre Raman probe will be discussed and general design considerations presented. Subsequently, various common geometries employed for enhanced Raman sampling are enumerated based on the types of waveguide fibres: multi‐fibre optodes, long‐pathlength capillary, microstructured photonic crystal fibre and other waveguide arrangements. Additionally, the relevant detection parameters are reviewed, such as target analyte, limit of detection, waveguide media and detection principle. The review also includes a brief summary of the advantages and limitations of various fibre Raman probes. Finally, the future work is discussed which will promote the reliability and the applicability of fibre enhanced Raman sensors. Copyright © 2017 John Wiley & Sons, Ltd.