Harnessing electromagnetic surface waves for optical sensing applications

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The excitation of electromagnetic surface wave can be acutely sensitive to the optical properties of the materials on either side of the interface to which these waves are localized. Consequently, electromagnetic surface waves are well-suited to optical sensing applications. Indeed, optical sensors based on surface-plasmon-polariton (SPP) waves -- which are electromagnetic surface waves supported by the planar interface of a metal and a dielectric material -- are at the forefront of label-free and real-time detection of analytes related to medical diagnostics, environmental monitoring and food safety. However, in addition to SPP waves, there are several other types of electromagnetic waves which seem promising for optical sensing applications. For examples, Dyakonov waves are supported by the interface between two dielectric materials, at least one of which is anisotropic; and Dyakonov--Tamm waves are supported by the interface between two dielectric materials at least one of which is anisotropic and at least one of which is periodically-nonhomogeneous. These and other types of electromagnetic surface waves could potentially yield optical sensors with sensitivities that exceed those associated with SPP waves. Furthermore, electromagnetic surface waves supported by periodically-nonhomogeneous materials are particularly appealing from the perspective of optical sensing applications because a multiplicity of these waves can be excited at a given frequency; potentially these multiple waves could be harnessed to improve sensitivities and specificities, and to detect more than one analyte at a time. Theoretical and numerical studies are proposed in order to investigate the suitability of electromagnetic surface waves supported by the planar interfaces of various anisotropic and periodically-nonhomogeneous materials for optical sensing applications. The materials are required to be porous to allow analytes to reach the interface. Prism-coupled and grating-coupled configurations will be investigated, with inverse homogenization techniques used to estimate changes in constitutive properties which result from infiltration by analyte-containing fluids. A key component of this work will involve research visits to the Department of Engineering Science and Mechanics at Pennsylvania State University, which is an internationally-renowned centre for excellence in theoretical and experimental aspects of electromagnetic surface waves and nanostructured materials. Funds are requested for two research visits which would enable the proposed project to be undertaken with maximum efficiency.