Raman spectra of copper phthalocyanine assisted by thick slab waveguide

Metal-cladding slab waveguide with millimeter scale thick guiding layer is applied to enhance Raman spectra of Copper phthalocyanine experimentally. Different from the usual strategy to create "hot spots" by designing sophisticated nanostructures with more and more narrow slits, we inclined to increase the distance between the two metallic cladding layers, i.e., the guiding layer thickness. Despite the risk of reducing the field intensity of the guided modes, the advantages are also obvious. First, the high mode density facilitates the coupling of the incident energy into the guiding layer. Secondly, near vertical incidence is possible, which can greatly simplify the optical setup and make the further lab on a chip application accessible. Finally, the polarization independent characteristics of thick waveguide also make a contribution to the Raman enhancement. Metal-cladding slab waveguide also provides a new possible method for detecting biological molecules.