Terahertz (THz) electromagnetic waves, locating at frequency range from 300 GHz to 30 THz, have received much attention as a new field for sensing and information communication technology. This reviews such THz science and technology and discuss recent advances. New industrial applications are now expected to grow in the sensing fields, especially for Bio, Medical Chemical and Pharmaceutical science.

Terahertz (THz) spectroscopy and imaging has been developed mainly based on THz time-domain spectroscopy (THz-TDS) using ultra-fast pulse lasers. Though THz-TDS is unique approach especially for the evaluation of physical properties of various kinds of materials, it is often pointed that the sensitivity and spatial resolution are not enough. In order to improve such insufficiencies, we developed near-field THz emitting spectroscopy imaging system. Fabrication of metamaterials and optimization of their structure provide higher sensitivity. By using ultra-thin film made of polydimethyl siloxane (PDMS) fabricated microflow channels stuck on GaAs as a THz emitter, a calibration curve was obtained for D-glucose solution in the concentration range lower than 0.5 M. This novel technique is expected to acquire physical properties for various kinds of liquid including biological samples, which were difficult to be evaluated by the conventional THz measurements.

Water molecules are well known to have extremely important functions in various biological reactions caused by their unique properties. Especially interactions between molecules via hydrogen bonds are observed in many situations, but direct measurement methods for finding themselves are limited. In this report, I present a method to determine the complex dielectric constant of a cell monolayer using terahertz time-domain attenuated total reflection spectroscopy combined with a two interface model. The complex dielectric constants of distilled water and HeLa cell monolayer between 0.25 and 3.5 THz come from Debye-type relaxation and Lorentz-type vibration dynamics of the water molecules and can be expressed as a superposition of the complex susceptibilities of slow relaxation, fast relaxation and intermolecular stretching vibration. This result also indicated the difference of such dynamics between distilled water and intracellular water clearly. Furthermore, I introduce a CMOS biosensor integrated circuit focusing on dielectric relaxations of biological water. Since this sensor can work as a near-field sensor, I demonstrated the measurement of intracellular water of cultured cell. I believe such a compact and easy sensor has a potential to open up the bio application in sub-THz region.

Recently, measurements of bio-related materials using terahertz technology have been attracted by many researchers. Among them, a terahertz chemical microscopy is one of the techniques that are not based on conventional terahertz spectroscopy, and has realized to visualize various types of chemical reactions in water solution. Here, detection mechanism of terahertz chemical microscopy was described, with followed by demonstration of label-free detections of bio-related materials.