Terahertz Biochemical Molecule-Specific Sensors

The terahertz (THz) spectrum is the focus of basic research in solid-state physics, chemistry, and materials science as well as applications in next-generation communications, far-infrared bolometer, bio/chemical-sensing, and medical imaging. This wavelength range is at the intersection between photonics and electronics, presenting tremendous opportunities to boost fundamental light-matter interactions enabled by plasmonic nanostructures, metamaterials, and inherent molecular vibrational modes, which occur on time scales of tens of femtoseconds to picoseconds. Recently, engineered metamaterials have presented unique platforms for sensing applications due to their ability to boost such light-matter interactions on the nanoscale and to their spectral selectivity in a wide range from the mid-infrared to the THz region. Their resonant response can be tuned to that of the intra- and intermolecular vibrational modes of target bio/chemical molecules. The emerging fields of highly sensitive and selective mid-infrared and THz spectroscopies based on metamaterials and plasmonic nanostructures are reviewed. Furthermore, practical applications of these next generation spectroscopic sensors are also discussed, where the sensor platforms will lead to a great impact in the advancement of ultrasmall-quantity detection of explosives, nondestructive inspection of hazardous materials, food safety, and conformational dynamics of biomolecules in their aqueous environment.