Terahertz Sensing Based on Metasurfaces

• Published in: Advanced optical materials Vol. 8; no. 3
• Main Authors: Beruete, Miguel, Jáuregui‐López, Irati
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.02.2020
• Subjects: biosensors; Detection; Ionizing radiation; Materials science; Metasurfaces; Microorganisms; Optics; Sensors; Spectrum analysis; terahertz sensors; Thin films; thin‐film sensors; Weak interactions (field theory)
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.201900721

The terahertz (THz) band has very attractive characteristics for sensing and biosensing applications, due to some interesting features such as being a non‐ionizing radiation, very sensitive to weak interactions, thus, complementing typical spectroscopy systems in the infrared. However, a fundamental drawback is its relatively long wavelength (10–1000 µm) which makes it blind to small features, hindering seriously both thin‐film and biological sensing. Recently, new ways to overcome this limitation have become possible thanks to the advent of metasurfaces. These artificial structures are planar screens usually made of periodic metallic resonators and whose electromagnetic response can be controlled at will by design. This design freedom allows metasurfaces to surpass the restrictions of classical THz spectroscopy, by creating fine details comparable to the size of the thin films or microorganisms under test. The strong field concentration near these small metasurface details at resonance makes them highly sensitive to tiny variations in the nearby environment, allowing for an enhanced detection more accurate than classical THz spectroscopy. The main advances in THz metasurface sensors from a historical as well as application‐oriented perspective are summarized. The focus is put mainly on thin‐film and biological sensors, with an aim to cover the most recent advances in the topic. The exciting topic of terahertz (THz) sensing using metasurfaces, is comprehensively addressed using a historical as well as an application‐oriented perspective. Three main groups are covered: thin‐film sensors, biosensors, and the latest manufacturing techniques, able to achieve extreme sensitivity values. The compendium here presented should serve to frame this rapidly evolving topic with an updated thorough historical view.