Harnessing electromagnetic surface waves for optical sensing applications

电磁表面波的激发可以对这些波局域到的界面两侧的材料的光学性质非常敏感。因此，电磁表面波非常适合光学传感应用。事实上，基于表面等离子体偏振(SPP)波的光学传感器处于无标签和实时检测与医疗诊断、环境监测和食品安全相关的分析物的前沿。SPP波是由金属和介质材料的平面界面支撑的电磁表面波。然而，除了SPP波，还有几种其他类型的电磁波似乎在光学传感应用中很有前途。例如，Dyakonov波由两个介质材料之间的界面支撑，其中至少一个是各向异性的；Dyakonov-Tamm波由两个介质材料之间的界面支撑，其中至少一个是各向异性的，至少一个是周期性非均匀的。这些和其他类型的电磁表面波可能会产生灵敏度超过SPP波的光学传感器。此外，从光学传感应用的角度来看，周期性非均匀材料支持的电磁表面波特别有吸引力，因为可以在给定的频率上激发多个这种波；潜在地，这些多个波可以被利用来提高灵敏度和特异度，并同时检测不止一个分析物。为了研究由各种各向异性和周期非均匀材料的平面界面支撑的电磁表面波在光学传感应用中的适用性，提出了理论和数值研究。这些材料要求是多孔的，以便分析物能够到达界面。将研究棱镜耦合和光栅耦合配置，使用反向均化技术来估计由于含有分析物的流体的渗透而导致的本构性质的变化。这项工作的一个关键组成部分将涉及对宾夕法尼亚州立大学工程科学和机械系的研究访问，该系是国际上著名的电磁表面波和纳米材料理论和实验方面的卓越中心。需要为两次研究访问提供资金，这将使拟议的项目能够以最高效率进行。

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.