Theoretical investigation of slab waveguide sensor using anisotropic metamaterial

A three-layer slab waveguide with air as a substrate, lossless dielectric as a guiding film, and anisotropic double negative material as a cladding is explored as an optical sensor for refractometry applications. The double negative material is assumed to have a negative electric permittivity and magnetic permeability only along the wave propagation direction. The sensitivity of a guided mode to the variation in the refractive index of air substrate is derived and studied for the first few guided modes. It is found that the sensitivity can be enhanced with decreasing the guided light frequency as well as the film thickness. The sensitivity can reach 100% for some waveguide configurations.