Enhanced Raman spectroscopy by a double cavity metal-cladding waveguide

Abstract

In order to double the mode density to increase the Raman scattering efficiency, a double cavity structure was introduced to the metal-cladding optical waveguide (MCW) chip. This novel double cavity MCW inherits all the merits of the MCW, such as free space coupling, large detection area, and polarization independence. Furthermore, attributed to the doubled mode density, more incident energy is coupled into the guiding layer and results in a larger enhancement of the Raman scattering. Since the distribution of the electric field is sensitive to the refractive index profile of the two cavities, the proposed structure can be further optimized to concentrate all of the energy to the sample cavity. Experimental verification via four liquid samples of a different refractive index is carried out in support of the above hypothesis.