Hollow core photonic crystal fiber surface enhanced raman probe

We demonstrate, for the first time to our knowledge, a hollow core photonic crystal fiber (HCPCF) surface-enhanced Raman probe. The probe consists of a HCPCF (also known as a holey fiber) with a layer of Au nanoparticles coated on the inner surface of the air holes serving as the substrate of surface enhanced Raman scattering (SERS). The sample being tested enters the air holes by the capillary effect. The excitation light is coupled into the fiber core from one end (measuring-tip) while the sample entrance is at the other end (probing-tip) of the fiber. The SERS signal scattered by the sample propagates through the fiber core back to the measuring-tip; then is coupled out of the fiber into the Raman spectrometer. The advantages of such probes include, the confinement of light inside the HCPCF provides a higher light efficiency; and the nanoparticles coated inside the air holes offers a larger interaction area for SERS. Both experimental results and theoretical analysis are presented and discussed.