Optical Sensing by Metamaterials and Metasurfaces: From Physics to Biomolecule Detection

Metasurfaces are planar or 2D forms of metamaterials made up of arrays of antennas with a subwavelength thickness. They have been rapidly developed in the recent years due to their ability to manipulate light-matter interaction in both linear and non-linear regimes at the nanoscale. Various metasurfaces display remarkable optical features, such as acute resonance, significant near-field enhancement, and suitable capacity to support electric and magnetic modes, on account of the strong light-matter interaction and the low optical loss. Due to these important properties, they can be used in several advanced optoelectronic applications, like surface-enhanced spectroscopy, photocatalysis, and sensing. This review reports on the recent progress of metamaterials and metasurfaces in molecular optical sensors. The principles that govern plasmonic and dielectric metasurfaces along with their features are outlined, supported by numerous examples. Then, the factors that result in a high Q-factor are presented in order to show that metamaterials and metasurfaces can be used for label-free sensing in a variety of detection mechanisms, including surface-enhanced spectroscopy, refractometric sensing, and surface-enhanced thermal emission spectroscopy via infrared absorption and Raman scattering, as well as chiral sensing. Finally, the challenges for future development are outlined.