Refractive Index Sensing with Anisotropic Hyperbolic Metamaterials

Metamaterials with hyperbolic dispersion based on metallic nanorod arrays provide a flexible platform for the design of bio- and chemical sensors and active nanophotonic devices that allow the incorporation of refractive-index-dependent materials into or on top of the metamaterial. In this Chapter, we describe sensing geometries with anisotropic materials and overview the refractive index sensitivity of the resonances of the metamaterial, in different regimes. The examples of various sensing applications for label-free analyte recognition, hydrogen detection and ultrasound monitoring will be described. A general strategy for maximising the refractive index sensitivity of nanorod-based hyperbolic metamaterials will be discussed and can be used as the basis for the design of new ultrasensitive chemo- and bio-sensors that outperform both surface-plasmon polaritons and localised surface-plasmon based transducers.